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WHAT DARE I THINK ?The Challenge of Modern Science

to Human Action and BeliefBy

JULIAN HUXLEYPROFESSOR OF ZOOLOGY

IN THE UNIVERSITY OF LONDON(KING'S COLLEGE)

CHATTO AND WINDUSLONDON


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First published October 1931Third edition January 1932First issued in the Phoenix Library

1933

Printed in Great Britain : all rights reserved


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PREFACEI HAD first of all thought of calling this littlework c Essays in Scientific Humanism. 5 Butthe word Essays has not a very fashionablesound to-day, while the word Humanism hasof late years been a good deal overdone,especially in the United States, where furtherit has acquired a slightly different connota-tion from that which it bear's in England.And, finally, I discovered that another bookhad recently been published with the phraseScientific Humanism in its title.So there was nothing to do but to try and

think of a new name. But whatever theactual title, what this book really contains issome Essays in Scientific Humanism. By sayingthat they are Essays I mean that they werenot all written on the same occasion ; but bysaying that they are essays in a particularsubject I mean that, in spite of this dis-continuity ofcomposition, they are definitelytied together by a common attitude of mind,

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WHAT DARE I THINK?a common approach. Finally, by using thephrase Scientific Humanism, I mean some-thing perfectly definite, which I hope willemerge clearly from Chapters IV. and V.I am sorry that the word humanism has beendistorted in the United States, on the onehand to mean a philosophical doctrine whichdoes not seem to me particularly humanisticin any recognized sense, and on the otherto serve as the name for an interesting brandof anti-supernatural religion. For in its un-distorted natural sense it is very useful ; andI see no other phrase but Scientific Humanismwhich could conveniently be used to crystal-lize that attitude of mind which it seems tome so imperative for the modern world tocultivate.The first five chapters are an amplificationof three lectures which I was invited to givebefore the Henry LaBarre Jayne Foundationin Philadelphia in January 1931. The planof them remains unaltered, but they havebeen considerably revised and amplified forpurposes of publication. Chapters IV. andV. can also be regarded as an amplification

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PREFACEofa lecture on Scientific Humanism deliveredin 1930 as President of the Social and Poli-tical Education League. The final chapterswere written as the Conway MemorialLecture which the Ethical Society invited meto give in October 1930. The ConwayLecture was, as is customary, reprinted inbooklet form and published by the Ration-alist Press Association. Portions of some ofthe other lectures have appeared in theContemporary Review, the Atlantic Monthly, andthe Tale Review. To the editors and pub-lishers concerned, I would like to tender mythanks for permission to reprint these articles.

In conclusion, I would like to thank theEthical Society, the Social and PoliticalEducation League, and especially the Trus-tees of the Henry LaBarre Jayne Foundationfor their invitations to lecture under theirauspices ; without these I should not havehad the stimulus to bring my scattered ideasinto some sort of order, and this book wouldnever have been written.

KING'S COLLEGE,LONDON, June 1931.


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TABLE OF CONTENTS

I Biology and the Physical En-vironment of Man Page i

II Biology and the Human Indi-vidual 45

III Man and His Heredity 74ry The Conflict between Science

and Human Nature 1 2 1V Scientific Humanism 149VI Science, Religion and Human

Nature 178VII Science and the Future of

Religion 224

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CHAPTER IBiology and the PhysicalEnvironment of Man

SCIENCES, like Empires, have their riseand their time of flourishing, though nottheir decay. Naturally, the order of their riseruns parallel with the complexity of theirsubject-matter. The physical sciences, beingthe simplest and most straightforward, werethe first to start their triumphant career.Some time in the future it will be the turn ofPsychology and of the elusive social sciences ;but at the moment the chief upward move-ment is that of biology.Looked at with the eye of the historian of

science, biology is seen to be just reaching theposition attained by the physico-chemicalsciences about the middle of last century.The phase in which that branch of sciencethen found itself was one in which a numberof different lines of investigation were being


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WHAT DARE I THINK?brought into intimate and often unexpectedrelations, in which several separate sets ofconcepts were being federated into a single,embracing scheme. Heat had come to beenvisaged, in Tyndall's phrase, as a c modeof motion ' ; the kinetic theory of gases tiedthe atoms of the chemist and the physicist'slaws oftemperature and pressure intom singlewhole. The generalizing ofelectro-magnetictheory ; the cohesion given to apparentlyunrelated subjects by the principle of theConservation of Energy ; the unity affordedto chemical facts by Mendeleeff's PeriodicLaw these were some of the ideas whichwere unifying physico-chemical science.

Similarly to-day in biology, the distribu-tion of hereditary qualities is seen to be aspecial aspect ofcytology, of the behaviour ofthe contents of the cell as seen with the neweye provided by the microscope. Mind andbody are revealed with ever-increasing clear-ness as two sides of the single biologicalreality, the organism, and not to be dis-entangled from each other. The ductlessglands which control the chemistry of our


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BIOLOGY AND PHYSICAL ENVIRONMENTbodies influence also the activity of our souls,adjust the development of our embryo selves,and are one of the important means by whichthe hereditary constitution impresses itselfupon our natures. Evolution is becomingmore intelligible as we link up the factsderived from the breeding-pen, the fossilsin the rocks, the behaviour of developingembryos and larvae, the laws of growth,the scientific study of natural history, themanoeuvres of the chromosomes, and thedistribution of animals and plants over theworld's surface, not forgetting to call in thediscipline of mathematics to our aid. Medi-cine and physiology are unified by ideasdrawn from evolution and experimental em-bryology. In brief, it is no longer possibleto be a physiologist or a biochemist, an eco-logist or a morphologist, a geneticist or asystematist (or at least not possible to do goodwork in any of these sub-sciences) withoutknowing a good deal of other branches ofbiojogy as well.Looked at from the standpoint of applied

science (and science always has its two as-


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WHAT DARE I THINK ?pects, its intellectual aspect as knowledge andits practical aspect as control), the presentposition of biology appears equally distinc-tive. Every science arrives at a stage duringwhich it makes its main broad contributionsto practical human affairs. Biology is clearlyon the verge of such a phase, while it isalready over for physics and chemistry, andpsychology and sociology cannot hope toreach it for perhaps another century.

I do not in the least mean to imply thatpractical inventions and applications of theutmost benefit and importance will not con-tinue to be made in the purely physico-chemical spherft for millennia to come. Ofcourse they will. But the chief kinds ofthings which man has wanted to ask of thiskind of science have already been granted.Man has wished to travel fast : he is alreadyapproaching the mechanical and physio-logical limits of speed. He has wished tocommunicate with other men at a distance,to capture and store the treasures ofsight andhearing ; and there are the telegraph andthe telephone, the radio and the gramophone,

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BIOLOGY AND PHYSICAL ENVIRONMENTthe photograph and the motion picture. Hehas wanted to fly in the air like a bird andswim under the water like a fish : he can anddoes. He has wished to be able to synthetizeuseful substances, to apply power with anintensity or speed a thousand-fold or million-fold of that possible to his own unaidedforces, to turn night into day at will, to matemachines do his mechanical work for him :he has already in large and indeed undreamt-of measure succeeded.But when we come to the biological field,the picture is very different. Most of us

would like to live longer ; to have healthierand happier lives ; to be ablfc to control thesex of our children when they are conceived,and afterwards to mould their bodies, intel-lects and temperaments into the best possibleforms ; to reduce unnecessary pain to a mini-mum ; to be able at will to whip up our,energies to their fullest pitch without later ill?effects. It would be pleasant to be able tomanufacture new kinds ofanimals and plantsat our pleasure, like so many chemical com-pounds, to double the yield of an acre of

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WHAT DARE I THINK?wheat or a herd of cattle, to keep the balanceof nature adjusted in our favour, to banishparasites and disease germs from the world.And there have been Utopians from Plato'stime and before it, most of whom havedreamt of controlling the stream of the raceitself not merely in its volume and quan-tity, but in its quality, so that humanitywould blossom into a new character.Of these obvious biological aspirations,how many have been fulfilled ? Anaesthetics

remove some of the grosser tortures of pain ;the average span of life is a few years longer ;some diseases have been stamped out orrendered less dangerous enemies ; there hasbeen some progress in the moulding ofour animals and crops and flowers. Butin general the wishes have remained onlywishes.On the other hand, enough knowledge isthere to make it clear that these biologicalwishes will soon be ripe for fulfilment. Andtheir fulfilment will obviously have moreintimate and more radical effects than thefulfilment ofchemical and mechanical wishes,

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BIOLOGY AND PHYSICAL ENVIRONMENTfor it will be affecting men directly instead ofindirectly.

I do not share the facile optimism whichsees in every increase of power, every fulfil-ment of a wish, a necessary good. Theknowledge provided by science is emotion-ally and morally neutral. And so is thepower of control which inevitably arises outof that knowledge. It is a tool, which likeother tools can be used for whatever ends itspossessor sees fit, whether good, bad or in-different. The effects of the industrial revo-lution and the subsequent inventions in thephysico-chemical sphere have not been sorosy as to warrant the belief still, it wouldappear, widely held that every invention isinevitably good, and that progress is auto-matic. Progress is only automatic in thesense that man, once he has reached a cer-tain stage in his development, cannot be keptfrom exerting his faculties and making newdiscoveries ; but it is not automatic in thesense of being a process inflicted upon us in-evitably from without, independent of ourefforts and ideals. Thus, while it is futile to


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WHAT DARE I THINK?try and turn back the tide, it is shallow follyto sit back complacently and watch its course.The true optimism is a tempered one.Change must come ; it can, on balance, begood ; it is our business to try to guide itand ensure that it shall be not merely changebut progress.An excellent example to our purpose isafforded by the biological sources of power.With the gradual exhaustion of coal and oil,better chemical methods, and the improve-ment of tropical agriculture, more and moreof the combustible sources of power, such asthe alcohols, will be got from the tropics,nfanufactured out of plants. This will meana revolution, a major shift in the economicsystem ofthe world. The last great economicrevolution was the industrial revolution ; andone of its effects was the growth of an indus-trial proletariat, which has not been withoutits disastrous results, disastrous politically andperhaps more, in the long run, socially andracially. If we are content in this forth-coming economic revolution once again toadopt a laissez-faire attitude, the world will

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BIOLOGY AND PHYSICAL ENVIRONMENThave on its hands a new proletariat, agricul-tural instead of industrial, tropical instead oftemperate, black and brown instead ofwhite ;and the results of its growth will be equallydisastrous.That is a good example, because it illus-

trates how the various aspects of a problemcan never be separated from each other.Power from tropical vegetation will neverbe a commercial proposition until economicpressure joins hands with chemical skill, withthe biologist's tricks for controlling weeds andinsect pests, the plant-breeder's manufactureof new types of organism, the agriculturist'scontrol of the soil ; and once it enters thecommercial field, it will immediately affectthe structure of the world's economic frame-work, the social life and, in the long run,the biological characteristics of the primitivepeoples of the tropics, and the whole raceand colour problem.In the brief space at my disposal I havenot the room, even if I had the knowledge,

to explore these far-reaching inter-relationsof biological progress with all other huma^i


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WHAT DARE I THINK?activities. I must content myself with re-minding my readers that they are alwaysthere, urging them to let their social andhuman imagination play round the conse-quences of scientific fact.Let us take a couple of examples at ran-

dom to point the moral, and then continuewith the plain tale of biology. It is clearlydesirable for man to be more healthy ; andwith regard to all the numerous brood ofgerm-caused diseases, the most obvious wayof attempting to provide more health is bygetting rid of the germ. I say the mostobvious way ; it may not prove to be themost practicable way. The League of Na-tions Commission on Malaria in Europe laiddown as its first principle that the radicalelimination of the malaria-transmitting mos-quito was not practical politics ; and therecan be no reasonable being who can imagineit possible to get rid of tuberculosis germs outof the world within the next thousand years.But, in some cases, we could eliminate thegerm, either locally, in the more civilizedcountries, or in some cases, even universally.

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BIOLOGY AND PHYSICAL ENVIRONMENTYellow fever is fighting a losing battle withMr Rockefeller ; it should, in the long run,be possible to wipe out the trypanosomes ofsleeping sickness ; scarlet fever and diph-theria, typhoid and enteric can be killedout or reduced to negligible proportions inreally civilized countries.

Well and good : but are all the resultsnecessarily good ? In the first place, withthe lifting of the rigorous hand of selection,the natural immunity to these diseaseswould decrease with their decrease. Beforemeasles were known in the South Seas,there was no biological necessity for theSouth Sea Islanders to possess any immunityto the disease, and there were among themall grades of inborn and inheritable resist-ance, from zero to moderately high. Whenit was introduced, it killed like the BlackDeath ; and by the elimination of those withleast natural resistance, the average resist-ance of the race has been considerably raised.And the converse will hold : with the banish-ing of a disease, the biological need for re-sistance will disappear, the less resistant will

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WHAT DARE I THINK?survive just as well as the more resistant, andthe average resistance of the population willgradually go down.What will then happen if the disease is re-introduced after several centuries of banish-ment ? It might be reintroduced during awar by an unscrupulous enemy ; it might getin accidentally ; the nation might declineand pay less attention to sanitation, so thatthe barriers to the entry of the disease-germswere lowered. And in any such event, thedisease would race through the country likeflame through dry grass, killing by the tensof thousands.What we have been saying applies to

specific resistance-immunity to one particulardisease-germ, not necessarily correlated withimmunity to any other disease, nor withgeneral vigour. But there is also general,non-specific resistance, something to do withgeneral health and vigour, the broad scaleagainst which the narrow scales of specificresistances are set up. Ceteris paribus, thestrong and generally healthy child or manwill survive, the weakling will succumb. And

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BIOLOGY AND PHYSICAL ENVIRONMENTif many diseases were banished from acountry, and matters otherwise left to them-selves, it is almost certain that there would bea lowering of the general vitality, stamina,and resistance of the population through thedisproportionate survival of the weaker ves-sels whom the diseases would have eliminatedmore ruthlessly than they did the general pop-ulation ; the population would be healthieras regards these particular diseases, but as arace it would have put its foot on the down-ward slope of degeneration.Or take another example, more spectac-ular, if more remote. The discovery thatsex is determined at conception by meansof the existence of two kinds of male cells,male-determining and female-determining, ofwhich the female-determiners are a little thebigger owing to their possession of an extrachromosome, opens the door to a possiblecontrol of sex. This could only be donethrough a separation of the two kinds ofmalecells, and the subsequent injection of one orthe other ; thus it is not likely to becomewidespread, even if it should become practic-

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WHAT DARE I THINK ?able, in our type ofsociety. But five hundredyears hence such interferences with naturemay be regarded in the same matter-of-factway as we regard interferences with naturewhich we now practise, like drinking the milkof other species of animal, using telephonesand aeroplanes, or wearing clothes. Andthen the sociological implications will begin.Should it be in the power of any parent toregulate the sex of his offspring at will ? Ifso, would not there be a great over-produc-tion of males ? If, on the other hand, it wereleft to the State, would there not again be agreat over-production of males, for purelymilitaristic reasons ? And, in such case, wouldthis not lead to what we might call a boot-legging production of girl children, privatelyand illicitly? For we can be sure that ifthere is a shortage of any essential com-modity, human or otherwise, the productionof that commodity will become immenselyprofitable.So we might go on ; but I have saidenough to show how important it is not towork in watertight compartments, but to try

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BIOLOGY AND PHYSICAL ENVIRONMENTto anticipate the consequences ofany change,the reverberations ofscience upon economics,recreation or social life.So much by way of introduction. In what

follows, the scheme I have adopted to bringsome order into my facts is itself a biologicalone. I have tried to describe some of theinfluences which biology is exerting or mightexert, first upon the tangible environment inwhich man lives ; next upon men andwomen as individuals ; then upon man as acontinuing race ; and last upon that in-tangible environment which man alone of allorganisms possesses, the tradition of thoughtand customs and accumulated ideas to which,just as inevitably and rigorously as to thephysical environment, his growing naturemust adapt itself.The most obvious way in which biologicalscience can have its practical say is in its effectupon the environment ofman. Not only canit influence this or that particular kind ofanimal or plant, encouraging one, destroyinganother, re-modelling a third, but it must becalled in to adjust the balance of nature.

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WHAT DARE I THINK?The balance of nature is a very elaborate

and very delicate system of checks andcounterchecks. It is continually being alteredas climates change, as new organisms evolve,as animals or plants permeate to new areas.But the alterations have in the past, for themost part, been slow, whereas with the arrivalof man, and especially of civilized man, theirspeed has been multiplied many fold : fromthe evolutionary time-scale, where change ismeasured by periods of ten or a hundredthousand years, they have been transferredto the human time-scale in which centuriesand even decades count.Everywhere man is altering the balance

of nature. He is facilitating the spread ofplants and animals into new regions, some-times deliberately, sometimes unconsciously.He is covering huge areas with new kinds ofplants, or with houses, factories, slag-heapsand other products of his civilization. Heexterminates some species on a large scale,but favours the multiplication of others.In brief, he has done more in five thou-sand years to alter the biological aspect

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BIOLOGY AND PHYSICAL ENVIRONMENTof the planet than has nature in fivemillion.Many of these changes which he has

brought about have had unforeseen conse-quences. Who would have thought that thethrowing away of a piece of Canadian water-weed would have caused half the waterwaysof Britain to be blocked for a decade? or thatthe provision of pot cacti for lonely settlers'wives would have led to Eastern Australiabeing overrun with forests of Prickly Pear ?Who would have prophesied that the cuttingdown of forests on the Adriatic coasts, orin parts of Central Africa, could have re-duced the land to a semi-desert, with the verysoil washed away from the bare rock ? Whowould have thought that improved communi-cations would have changed history by thespreading of disease sleeping sickness intoEast Africa, measles into Oceania, verypossibly malaria into ancient Greece ?These are spectacular examples ; butexamples on a smaller scale are everywhere

to be found. We make a nature sanctuaryfor rare birds, prescribing absolute security


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WHAT DARE I THINK?for all species ; and we may find that somecommon and hardy kind of bird multipliesbeyond measure and ousts the rare kinds inwhich we were particularly interested. Wesee, owing to some little change broughtabout by civilization, the starling spreadover the English countryside in hordes. Weimprove the yielding capacities ofour cattle ;and find that now they exhaust the pastureswhich sufficed for less exigent stock. Wegaily set about killing the carnivores thatmolest our domestic animals, the hawks thateat our fowls and game-birds ; and find thatin so doing we are also removing the brakethat restrains the multiplication of mice andother little rodents that gnaw away thefarmers' profits.

In brief, our human activities are every-where altering nature and its balance,whether we realize it or no, and whether wewant to or no. Ifwe do not wish the altera-tions to be chaotic, disorderly and oftenharmful, we must do our best to controlthem, and constitute new balances to suitour purposes.

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BIOLOGY AND PHYSICAL ENVIRONMENTThe first and most obvious department of

control is the conservation of nature and itsresources. It is extremely easy to kill thegoose that lays the golden eggs ; and whenthe goose is a wild species, once killed it isgone for ever. The Maoris killed the Moas,of which a number of different kinds used toinhabit New Zealand, for their meat. Sailorsexterminated the Great Auk. The final ex-tinction of the Mammoths was in all proba-bility caused by the attacks of our Stone Ageancestors. The white man reduced the Bisonfrom an abundance comparable with theabundance of zebra or gnu in Africa until to-day its precarious remnant has to be lookedafter like a museum specimen. The Fur Sealsof the Pacific were brought by indiscriminateslaughter to the verge of disappearance, andwere only saved by international agreement.The huge hordes of whales of the northernseas were harried into insignificance ; andnow there is danger that their southern rela-tives will follow suit. Of the elephants ofAfrica, according to Major Kingston, ten percent, are killed every year. The marvellous


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WHAT DARE I THINK?guano deposits of the west coast of SouthAmerica were being exhausted, and haveonly been saved by the careful regulations atlast imposed by the Peruvian Government.

If we want wild creatures to go on pro-viding us with oil, furs, fertilizers, ivory, meator sport, we must regulate their affairs as wewould regulate a business. We must knowwhere and when they breed, howmany youngthey have, how long they take to grow up,what their natural mortality is, and muston the basis of this knowledge adjust our ex-ploitation so that it only skims off the naturalincrease. This has been done for someanimals ; it can be done for those others thatare now in danger'of our reckless methods.But as well as the preservation ofparticular

species, there is the preservation of nature asa whole to think about. If we do not takecare, we shall find civilization infiltrating allbut the most inhospitable parts of our planetand leaving no regions in their pristine andexhilarating state. It is so easy to kill outgame, leaving a country still untamed butsadly barren ; to dot the wilderness with

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BIOLOGY AND PHYSICAL ENVIRONMENTstraggling outliers of industrialism, leavingit neither wild nor yet civilized ; to cut downforests without making provision for replace-ment, leaving scrub forests of second growth,as over so much of the United States, or evenonly bare hillsides ; in brief, to mix natureand civilization so that the fine essence ofthe one is destroyed, of the other not fullyrealized, and the net result an unsatisfyingcompromise.The remedy is conscious planning. Noone supposes that the game animals of Africacan everywhere remain as they are, thatforests and jungles will not often need to be,cut down, or replanted artificially and scien- ;tifically, that many swamps should not bedrained, many stretches of sea-coast turnedinto holiday towns. But we can delimitdifferent areas for different purposes. Mandoes not live by bread alone. There is his)need for solitude to consider, and his scien-ftific interests ; there is the recreation andrefreshment afforded to him by nature, andthe unique excitement and interest of seeingwild creatures.

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WHAT DARE I THINK?These needs can all be met ifwe only take

them in time. There are different balancesof nature and civilization, each of them ad-mirable in its way, whose preservation can bedeliberately planned. We can plan the cityso that it provides beauty, ease of movement,varied activities, and a sense of civic pride.We can plan the small town so that it pro-vides a centre of life for its area, yet withoutspoiling the zone cf country round it. Thereal countryside is profoundly artificial, withnature tamed by man ; but it represents aparticular balance, which has its own uniquepossibilities ofbeauty and interest, and it canbe guarded from unwarranted intrusions, itspeculiar attractions can be preserved, itsdevelopment can be guided. The half-wildcountry of moor, mountain, marsh, forest orsea-shore can be either entirely reclaimed, orkept entirely unspoilt.When we come to setting aside definitetracts of land for other than material needs,can plan them with precise aims in view,

areas should be set apart as specimensof nature, just as we preserve specimens of

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BIOLOGY AND PHYSICAL -ENVIRONMENTinteresting animals and plants in our mu-seums. These are Nature Sanctuaries, towhich access should only be sparingly ac-corded, and then mainly for purposes ofscientific study. The prime object here is tokeep the original balance as unaltered as pos-sible. Then there are National Parks, wherenature is conserved not in the interests of theenquiring scientific spirit of man, but in theinterests of his love of natural beauty andneed ofwildness and solitude. The essentialsofnature must here be preserved, but a com-promise will often have to be struck with theneed for making nature accessible. Allgrades of naturalness can be preserved inNational Parks, from the unspoilt wildness ofthe Grisons or the Yosemite to the partially-tamed beauties of Sussex downland or theNew Forest. And, finally, we can providescheduled areas ; for these, while recog-nizing that their prime purpose is utilitarian,we can introduce regulations which willensure that their wild life and their otherattractions are interfered with as little as maybe, and that their possibilities of providing

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WHAT DARE I THINK?recreation and beauty are made plentifullyavailable. '^In addition to these main categories, wemay establish reserves for special purposesfor bird life, for the preservation of rare orbeautiful plants, or even for strange humanbeings like the pigmies. But in every case wemust have in mind just what we want to do,and carry out our plans accordingly. Inalmost every case some degree of control willbe needed to preserve this or that balance,for the original balance of nature is gone, de-stroyed by the mere presence of man onearth ; and even in the remotest regions itwill rarely be enough to leave everything tonature, for nature almost everywhere hasalready been in some measure modified byman, and is therefore already to that extentartificial. I will give but one illustration.The traveller through East Africa naturallythinks that its great stretches of thorn-scrubcountry are a part of primeval nature. Butin great part they exist by virtue of humaninterference ; if it were not for the blackman's cattle, and his habit of burning the

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BIOLOGY AND PHYSICAL ENVIRONMENTbush, they would be woodland, of quite adifferent character. Those who want otherexamples will find them in abundance inRitchie's interesting book, The Influence ofMan on Animal Life in Scotland. Even to pre-serve nature, we need to have a knowledgeof the machinery by which the balance ofnature is adjusted ; and for that we needa well-developed science of ecology, thatbranch of biology which studies the relationsof wild organisms to each other and totheir environment.The other province of ecological biologyis its aid, not in preserving nature as nearher original self as possible, but in control-ling and remoulding her to suit the economicpurposes of man.

Agriculture is the chief of man's effortsat the biological remodelling of nature. Ifwe reflect that agriculture is less than apaltry ten thousand years old out of the threehundred million years that green plants havebeen on earth, and that apart from forestfires and perhaps a little occasional clearing,there had before that been no human inter-

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WHAT DARE I THINK?ference with the natural mantle ofvegetation,we begin to grasp something of the revolutionwrought by this biological discovery.But agriculture is, if you like, unnatural ;

it concentrates innumerable individuals of asingle species and always, of course, a par-ticularly nutritious one in serried ranks,while nature's method is to divide up thespace among numerous competing or com-plementary kinds. Thus it constitutes notmerely an opportunity but a veritable invita-tion to vegetable-feeding animals, of whichthe most numerous and most difficult to con-trol are the small, insinuating and rapidly-multiplying insects. And the better andmore intensive the agriculture, the richerbecomes the banquet, the more obvious theinvitation. Shifting cultivation, with poorly-developed crop-plants and plenty of weeds,is one thing ; but mile upon square mile oftender, well-weeded wheat or tea or cottonoffers the optimum possibilities for the rapidmultiplication and spread of any species ofinsect which can take advantage of man'sgood nature towards his kind.

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BIOLOGY AND PHYSICAL ENVIRONMENTFinally, man's insatiable desire for rapid

and easy transit has capped the trouble.Evil communications, we all know, corruptgood manners : it is not generally realizedhow much good communications have doneto corrupt the balance of nature.By accident or intention, animal and plant

species find their way along the trade routesto new countries. They are in a new en-vironment, among a new set of competingcreatures to whose particular equilibrium ofstruggle they are not adapted. In such cir-cumstances, the majority fail to gain a foot-hold at all ; some survive on sufferance ; buta few find in the new circumstances a releaseinstead of a hindrance, and multiply beyondmeasure. The release may be a release fromcompetitors, as when the mongoose was in-troduced into one of the West Indian islands,or, more frequently, a release from enemies,whether large and predatory or small andparasitic.Then it is up to the biologist to see whathis knowledge can do. Can he, by studyingthe pest in its original home, discover what

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WHAT DARE I THINK?are tne other species that normally act aschecks on its over-multiplication, make surethat, if he imports them to the new country,they will not there change their habits andturn into pests themselves, then successfullytransport them, and breed them and letthem loose in sufficient numbers to bring theenemy of the crops down to insignificance ?Sometimes he can. Let me give twoexamples. On Fiji, coconuts have for sometime been one of the staple products. Somefew decades ago, the plantations on one ofthe main islands were reduced to nutless,leafless poles. That was bad enough ; butthen, after the war, the plague began toappear on the other and larger main island.The men are still alive and active who

brought prosperity back to Fiji. It hadalready been discovered that the cause ofthe trouble was a little moth very beautiful,with violet wings whose grubs devoured theleaves of the palm-trees ; and it prospered soalarmingly because in Fiji it had no parasiteenemies. Three biologists were appointed tofind a parasite. They searched the remote

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BIOLOGY AND PHYSICAL ENVIRONMENTcorners of the Pacific. At last they found, inthe Malay States, not the same moth, but aclosely-related species, which was providedwith its natural complement of parasites,notably a kind of fly. It was not easy tobring the parasites the long distance to Fiji,for they do not hibernate, and so must befed and tended all the time. They had tobe provided with living moth-caterpillars,and these in return had to be provided withnewly-sprouted coconuts, grown in specially-built cages. As there was no direct com-munication from this part of the MalayStates to Fiji, a steamer had to be charteredfor the voyage.By these means, 300 precious parasitic flies

were in 1925 safely landed in Fiji. Thesewere bred on the caterpillars of the Fiji coco-nut moth, and within twelve months hadincreased to 32,000. Then the liberation ofthe parasites began, and they went to theirwork with such gusto that by 1928 at leastfour-fifths of the coconut-moth caterpillarsof Fiji were parasitized, and therefore cameto nothing. By 1929 the coconut moth,

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WHAT DARE I THINK?which threatened to ruin the archipelago,had become reduced to the status of a minornuisance. Man had readjusted the environ-ment, whose balance he had in the firstinstance upset.Then there is the Prickly Pear in EasternAustralia. I remember once hearing a lec-ture by Dr Tillyard, now in charge of pestcontrol and related problems in Australia.After he had been talking of the Prickly Pearfor a bit, he drew out his watch. c It is sevenminutes/ he said, c since I began discussingthis subject ; during that time another sevenacres of Australian land have been coveredwith this impenetrable and useless scrub. 5That, however, was five or six years ago. Inthe meanwhile, the research scheme begunby the Australian Commonwealth in 1920has matured. At their research station estab-lished on the American continent originalhome of the prickly pear and other cactievery possible enemy of the cactus was triedout ; and at last a mixed team was sent toAustralia a caterpillar to tunnel throughthe c leaves ' (which are really the prickly

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BIOLOGY AND PHYSICAL ENVIRONMENTpear's stems), a plant bug and a cochinealinsect to suck its juices, and a mite to scarifyits surface. These were the Four Arthropodsof the prickly pear's Apocalypse ; instead ofincreasing any longer in Australia, it is nowhalted, and in many places the thickets aremelting away under the combined attack.One could multiply instances. How thesugar-cane of Hawaii was saved from itsweevil destroyers ; how the destruction ofNorth American forests by Gipsy-moths washeld in check ; how an attack is beinglaunched upon the mealy-bugs that are sucha pest to Kenya coffee, by massed battalionsof lady-birds, bred up on a generous rationconsisting of chopped eggs, cream, marmite,honey, and radio-malt. To cope with all thedemands for anti-pest organisms, a veritableindustry has sprung up. There exists nearSlough a Government establishment, usuallynicknamed the Parasite Zoo, whose primefunction is to breed up the supply of pest-parasites demanded by the British Empire.

All the spectacular successes have beenachieved when a pest has invaded new


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WHAT DARE I THINK?territory ahead of its enemies. Even in suchcases, however, success has not always beenattained. Sometimes this may be due to theweakness ofhuman nature : there have beenBoards of Pest Control which were not tooanxious to find their occupation gone with thegoing of their particular pest. But leavingsuch non-biological or hyper-biological con-siderations on one side, there have been manypests which have so far baffled research. Oneneed only think of the invading thickets ofblackberries in New Zealand ; of the diseasethat has recently been blighting the elms inits march across Western Europe ; of thespread of the European corn-borer over theUnited States to the great detriment of themaize crop ; ofthe permanent pest ofrabbitsin Australia.Such being the difficulties ofthe work when

reduced to its simplest terms, we should ex-pect to find them far more severe when thepest is an old-established inhabitant of thecountry. For then it will already possess itsfull complement of enemies and parasites,and exist in a natural equilibrium with them,

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BIOLOGY AND PHYSICAL ENVIRONMENTso that we can have little hope of causing aspeedy reduction by the mere liberation of aparasite. And it has become a pest throughman providing, in his own person or in thatof his domestic animals or plants, a new andsusceptible source of food. Problems of thistype are set to us by malaria, spread by in-digenous mosquitoes ; human sleeping sick-ness and nagana disease ofcattle, transmittedby tsetse-flies ; plague, dependent for itsspread upon the ubiquitous rat.

In British Africa alone, areas aggregat-ing many times the size of Great Britain areinfested by tsetse, and so made uninhabit-able by any native population save huntingnomads, since all settled native culture in-volves the keeping of cattle. In some places,the issue is whether man or the fly shalldominate the country ; at the presentmoment the fly's dominion in Tanganyika istwice the size of man's. The disease-agentswhich it transmits, the blood-parasites calledtrypanosomes, live normally in the blood ofgame and other wild animals, and do themno harm, since host and parasite have become

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WHAT DARE I THINK?mutually adapted through millennia ofselec-tive adjustment ; but man and his beasts arenew hosts, and are without any such adaptiveresistance. In such a case, the best remedyseems to be to alter the whole environment insuch a way that the tsetse can no longerhappily live in it. Most tsetse-flies live inbush country. They cannot exist either inquite open country, or in cultivated land, orin dense woodland or forest. So that eitherwholesale clearing or afforestation may getrid of them. Or it may be possible that achange of conditions will favour one of thelocal parasites and so bring about a newbalance between the fly and its enemies.And by studying the precise habits of thecreature, efficient methods of trapping maybe devised.That pests of this nature can cease to be

serious is shown by the history ofmalaria andof plague. In various parts of Europe andAmerica, these diseases, once serious, havewholly or virtually died out. And this hashappened through a change in human en-vironment and human habits. Take plague.

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BIOLOGY AND PHYSICAL ENVIRONMENTModern man builds better houses, clearsaway more garbage, segregates cases ofinfectious diseases, is less tolerant of dirt andparasites, and in fine lives in such a way thathis life is not in such close contact with thatof rats. The result has been that rats havefewer chances of transmitting plague to man,and that the disease, if once transmitted, hasless chance of spreading. With regard tomalaria, although it is essential for quickresults to utilize all the implications of Ross'and Grassi's great discovery that the diseaseis transmitted by mosquitoes, yet as a matterof history agricultural drainage, cleanlinessand better general resistance, have, in manyplaces, done as much or more than deliberateanti-mosquito campaigns to reduce or banishthe disease.

So, too, typhus disappears with the spreadof cleanliness, typhoid with the arrival of agood water supply ; and tuberculosis is morelikely to be reduced by changed habits asregards fresh air, nourishing diet, and thepublic attitude to clean milk, than by anydirect attack upon the tubercle bacillus.

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WHAT DARE I THINK?All the methods of which I have spoken

have this in common that they attempt tobreak the power of a pest by altering the restof the environment, by directly or indirectlyinterfering with the balances of existingnature, so that the conditions shall nolonger be so favourable for the obnoxiousspecies.But we could attack the problem from

another angle. We could alter the verynature of Nature, changing the balance, notby changing the conditions, but by chang-ing the inherent qualities of the organismsinvolved. For instance, instead of tryingto attack a pest by means of introducingenemies, or altering the environment inwhich it has to carry on its operations, we canoften deliberately breed stocks which shall beresistant to the attacks of the pest. Thus wecan now produce relatively rust-proofwheat ;and the Dutch have given us spectacularexamples of what can be accomplished bythe thoroughgoing application of Mendelianmethods, by crossing a high-yielding butdisease-susceptible sugar-cane with a related

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BIOLOGY AND PHYSICAL ENVIRONMENTwild species which is disease-resistant, and,in spite of the fact that the wild parentcontains no trace of sugar, extracting fromthe cross after a few generations a disease-resistant plant with an exceptionally highyield of sugar.Ecology here joins hands with genetics.And with genetics we may conclude our

chapter, for it offers the prospect of the mostradical transformations of our environment.Cows or sheep, rubber-plants or beets, repre-sent from one aspect just so many livingmachines, designed to transform raw ma-terial into finished products available forman's use. And their machinery can beimproved. Modern wheats yield severaltimes as much per acre as the unimprovedvarieties grown by early and primitive agri-culturists ; and of late years, through thedeliberate breeding of new types, the rangeof successful wheat cultivation has beenextended nearly a hundred miles nearer thepole, and far into areas previously consideredsemi-desert.Modern cows grow about twice as fastD 37


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WHAT DARE I THINK?as the cattle kept by primitive tribes ; andwhen they are grown, produce two or threetimes as much milk in a year. This hasthrown a new strain on the pastures uponwhich they feed, for the cow eventuallydraws its nourishment out of the soil, and ifthe animal machine for utilizing grass is im-proved, the plant machine which is respon-sible for the first stage of the process, ofwork-ing up raw materials out of earth and air,must be improved correspondingly. Accord-ingly research is actively in progress not onlyto discover the best fertilizers for grass, but tomanufacture new breeds of grass which shallbe as much more efficient than ordinary grassas a modern dairy beast is than the aboriginalcow.Of course, if we choose to give rein to ourspeculative fancy, there is hardly a limit tothe goals to be set to deliberate breeding.Evolution is one long sermon on the text ofthe infinite plasticity of living matter. Tem-perament as well as anatomy, habits as wellas structure, can be moulded by selection.We can breed out high-thyroid and low-

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BIOLOGY AND PHYSICAL ENVIRONMENTthyroid strains of doves, or tame and savagestrains of rats, which depend on definiteMendelian differences as much as do blue-eyed or brown-eyed strains ofhuman beings,or the tall and dwarf pea-plants of Mendelhimself. Ifwe wished, we could undoubtedlyinflict upon other felines what we havealready inflicted upon a number of breeds ofdomestic cat namely, placid amiability inplace of spitfire ferocity ; and we couldobtain tigers which, in actual fact, and notonly in Mr Belloc's verse, were c kittenishand mild. 3 But such speculations belong tothe remoter future ; and I leave my readersto pursue them in the pages of Mr Wells'Men Like Gods or Mr Stapledon's First andLast Men. They serve to remind us, how-ever, in moments of discouragement in ourmore immediate and pedestrian tasks, of thepossibilities that do exist, and of the follyof impatience in a world which achievesits real results not in tens but in thousandsof years.

If I have chosen to concentrate largelyupon the subject of pests, it is because it

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WHAT DARE I THINK?brings out so clearly the intricate inter-relationships of what we usually call thebalance of nature, and the possibility ofstriking achievements, provided we build upthe ecological science which alone can giveus the necessary knowledge. There areplenty of other topics which coldd as fruit-fully have been explored. Selective breedingI have just touched upon. I fiave hardlymentioned the sea, although it covers three-fifths of the earth's surface, and is inhabitedin three dimensions instead of only two likethe land. With the invention by ProfessorHardy, of Hull, of the continuous plankton-recorder, we now can get a quantitativeknowledge of the floating microscopic plantsand animals that are at the basis of all thefood-economics of the sea ; with its aid wecould and should prepare a map of thesea, analogous to a vegetation map of theearth, showing the zoning of the rawmaterials available for fish and whales,and of other larger and more humanlyinteresting life.Then many microscopic forms of life them-

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BIOLOGY AND PHYSICAL ENVIRONMENTselves produce valuable materials : we couldbegin the deliberate cultivation of usefulspecies of diatoms or filamentous algae orprotophyta, with a view eventually to grow-ing them on a large scale in enclosed baysor arms of the sea.Again, now that Baly has been able to

produce sugar (albeit only a trace) out ofnothing but water, salts, air and light, wecan look forward to steady progress in thedirect synthesis of food-stuffs from inorganicmatter. But progress is bound to be slow,and meanwhile we can set our existingmethods in order by not wasting any of theessential raw materials used in nature's wayof food manufacture by the agency of greenplants. At the moment, the world is squan-dering its capital of available phosphorusand nitrogen certainly as fast as GreatBritain is spending her accumulated financialcapital. The chiefway in which we waste itis by discharging our sewage into the sea,whence but little material ever returns toland. Nitrogen can be replaced out of theunlimited resources in the atmosphere, now

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WHAT DARE I THINK?that we have found how to tap those re-sources and turn them into available form.But there appears to be no reserve source ofphosphorus : unless we want our descendantsto starve, we must plan the conservation ofthis essential element.These few examples must suffice to show

the kind ofcontrol which man is just realizinghe could exert over his environment. Butthey are enough to give us a new picture thepicture of a world controlled by man. Itwill never be fully controlled, for man cannotprevent earthquakes or eruptions, control theseasons or the length of day, change theclimate of the Poles, stop hurricanes or oceancurrents, or tap the resources of the oceanfloor ; but just as the control exercised byman to-day is far greater than that exertedby any other animal species, so the futurecontrol of man will enormously exceed hispresent powers ; and even where he does notcontrol, he will often, within limits, be regu-lating or guiding the course of nature ; andwhere he does not guide, he will at least beexploiting in a conscious and deliberate way.

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BIOLOGY AND PHYSICAL ENVIRONMENTThe world will be parcelled out into what isneeded for crops, what for forests, what forgardens and parks and games, what for thepreservation of wild nature ; what grows onany part of the land's surface will grow therebecause of the conscious decision of man ;and many kinds of animals and plants willowe not merely the fact that they areallowed to grow and exist, but their charac-teristics and their very nature, to humancontrol.The sea will be mapped in new ways,

exploited scientifically without waste, andmuch of it, almost certainly, will be farmedor cultivated as we cultivate the land, to givea larger yield. And disease-germs, pests,noxious weeds and vermin, will be in largemeasure abolished or, at least, under thethumb of a scientific humanity.******But an organism is an interaction between

the nature of its own protoplasm and thenature of its environment ; and to concen-trate too exclusively upon the environment isto leave the greater half undone. In what

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WHAT DARE I THINK?follows, I must try to give some idea of theeffect which biology may have upon humanprotoplasm, whether embodied in separatedeveloping individuals or flowing onwardsin the single evolutionary stream of therace.

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CHAPTER IIBiology and the Human

Individual

THE human individual is in certain im-portant respects the most complicated bitofmachinery in existence. And its machineryis, of course, biological. It is thus clearlyimpossible to survey the relations betweenbiological science and the human organismin a single chapter ; for to do this properlywould require a treatise on physiology, atreatise on psychology, a treatise on embry-ology, and a treatise on medicine. All I canhope to do is, taking a great deal of know-ledge for granted, to show some of the waysin which the advance of biological know-ledge may be expected to react upon ourattitude to our control of our individualhuman selves.

I do not want my readers to become angrywith me at the outset. So, as I know what

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WHAT DARE I THINK?clouds of philosophic wrath can rise at thesuggestion that man is a machine, I supposeI must devote a few words to justifying thatharmless but necessary phrase.Man is, from the external viewpoint ofphysical science, a bit of machinery. Fromanother aspect, he is a spiritual being, whoseemotional and intellectual activities, sincethey occur in the realm of consciousness andare non-spatial and non-material, are in adifferent order of existence. By some means,these two aspects are interdependent : it isthe task of the future to determine preciselyhow. But this is irrelevant to our presentpoint, which is, that in so far as man is madeof matter an indisputable if often incon-venient fact he obeys the same laws asother material aggregations. The conserva-tion ofmatter, the conservation ofenergy, thelaws of chemical combination, the orderlysequence of events which we sum up as theprinciple of cause and effect the progressof biology during the last hundred years hasshown that these generalizations apply to anincreasing number of aspects of living matter


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BIOLOGY AND THE HUMAN INDIVIDUALas well as to matter which is not living, hasenormously narrowed the field of life-pro-cesses in which they might possibly not hold,and has thrown the burden of proof thatthey may perhaps not be universally validupon those who oppose this view. It issimply this applicability of the same laws tothe same aspects, both of living and non-living matter, which I have in mind when Ispeak of an organism, human or otherwise,as a machine ; and it is at least fair to saythat it is not only the general workinghypothesis of most biologists, but a workinghypothesis which continues to justify itselfby ever new fruits.Most people at the word machine have a

vision of something made of steel and util-izing the principles of mechanics to do itswork. But you may have chemical machinesor electrical machines. An electric cell is justas much a bit of machinery as a steam-hammer, a sulphuric acid plant just as muchas a printing press. And the organism,though it contains machines which are purelymechanical in the classical sense, like the

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WHAT DARE I THINK?levers provided by the skeleton, is in themain a piece of chemical machinery, and,further, one whose chemistry is of an appall-ing order of complexity compared with mostofthe chemistry studied in ordinary chemicallaboratories.The working hypothesis of most biologists,

then, is simply that man, like other organ-isms, has an aspect in which he can bestudied and controlled as a piece ofmachinery

a very complicated piece of machinery,largely chemical, with great powrers of self-regulation (they too dependent upon theirown particular mechanisms) but none theless a piece of machinery. If they did nothold this working hypothesis, they wouldnot be able to continue hoping for successfulresults from their work.******During the last two centuries, and notablyduring the last seventy or eighty years, therehas been a great deal of progress in under-standing and controlling human machinery.But it has been limited in two main respects.It has been confined to the period after


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BIOLOGY AND THE HUMAN INDIVIDUALbirth, when the plasticity of the organismhas been largely lost, and only minor changescan be induced ; and it has concerned itself,not unnaturally, much more with diseasethan with health, much more with remedy-ing marked defects or departures from thenormal, than in raising the normal to itsoptimum.

Let us consider these two aspects of thequestion : and first, the possibility of attack-ing and bringing under control that earlierand more astounding part of our life-historyin which a human body is produced out of atiny speck of protoplasm.The human being, like other organisms,must develop : like other higher animals, hemust develop from a fertilized egg a meresingle cell, microscopic in size and simple instructure. In his development, again likeother animals, he passes through two mainphases. There is an early phase, duringwhich, without much growth, the main planof the future human being is laid down, anda later phase, during which great growthoccurs and details are filled in. During the

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WHAT DARE I THINK?first phase, development takes him from thestate of a mere egg to that of a vertebrate,from a single spherical cell to an organismwith head, brain, heart, digestive tube, limbs,skeleton, muscles, kidneys, and other neces-sary organs. During the second, the organsbegin to work in their characteristic way,the mere vertebrate remoulds itself to fit itselffor land life, reveals itself as a mammal, aprimate, a human being ; the ductless glandsexert their action, and very considerablechanges of proportion are brought about.Now, in lower vertebrates, such as frogs,newts and fishes, in which the eggs are laidfree in the water, biologists have found itpossible to play a great many tricks upondevelopment. They have been able to makea single egg produce twins or double mon-sters, either by mechanical constriction or bydepriving it of oxygen at a certain criticalstage. By exposing eggs to a temperature-gradient they have been able to make themgrow into embryos with big heads and smalltails, or vice versa, or with one lateral half ofthe body bigger than the other, according to

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BIOLOGY AND THE HUMAN INDIVIDUALthe direction of the gradient. They can re-duce and even abolish the organs in the frontof the head by exposing certain early stagesof development to narcotics, and can exag-gerate their size by stimulants. In frogs andtrout, by delaying fertilization, they havebeen able to make eggs that ought to producefemales, prodiice males instead (but, as theystill contain the chromosomes offemales, theycan produce nothing but female offspring inthe next generation).

All this is by treatment in the stages beforedefinitive vertebrate ground-plan is laiddown. But after this, all sorts of control arestill possible. By the comparatively crudeprocess of grafting, limbs and organs can beshifted from their proper positions, and madeto grow almost anywhere the experimenterwishes. By exposing the young animal todifferent conditions, the functional responseof its organs can be brought into play in verydifferent ways : for instance, a young sala-mander can be made to produce gills severaltimes as big and branched as normal bykeeping it in poorly-aerated water, while its

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WHAT DARE I THINK?brother, kept in water artificially over-oxygenated, will have gills that are merestumps.By removing the animal's ductless glands

at a very early stage, profound modifica-tions of development can be made to occur.Tadpoles with either their thyroid or theirpituitary removed will never turn into frogs ;the presence of the pituitary seems to benecessary for the full development of thereproductive organs as well as for propergrowth ; and so on. Conversely, giving anexcess of the secretion of this or that glandmay have striking effects, and the earlier thetreatment begins the more striking it will be.Young tadpoles given the right dose ofthyroid will develop into frogs no bigger thanhouse-flies, and with abnormally small limbs.Then we are just beginning to know howto influence the rate of growth. Certainsulphur-containing compounds have beenshown to stimulate growth in a markedway, and certain others to slow it down, thestimulating or retarding effect depending onwhether the compounds are not or are oxi-

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BIOLOGY AND THE HUMAN INDIVIDUALdized. What Is especially interesting is thatthey appear to influence that sort of growthwhich depends upon the multiplication ofcells, and not that which depends upon thecells' increase in size, so that by their use weought to be able, not only to control growthin general, but to affect the growth of someorgans more than others and so alter theanimal's proportions.

This is all very interesting theoretically,but how could it be applied to organismswhere, as in man, all the early and mostsusceptible stages of development are safelylocked away in the mother's womb ? Here,again, various possibilities suggest them-selves. Many of my readers will rememberhow Mr Haldane in his Daedalus envisagedthe possibility of * ectogenesis/ or the bring-ing up of babies in incubators instead of intheir mothers' bodies. We are a long wayfrom realizing that possibility, and yet, in theshort space of time since he wrote, the firststep has been successfully taken. ProfessorWarren Lewis, of Baltimore, has succeededin cultivating rabbits' eggs outside the body,

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WHAT DARE I THINK?from a moment immediately after fertiliza-tion to about a week later, when they haveenlarged considerably and the embryo isshowing the beginnings of organization. Hehas even recorded their development on thecinematograph ; and it is one of the mostastonishing spectacles to see, on the speeded-up film, the processes of cell-division, oforganization, of growth, which have neverbefore in any mammal taken place in thelight of day, going on in the unfamiliar en-vironment of a drop of nutrient fluid in aglass dish just as happily as in the darkrecesses of the Fallopian tube, just as regu-larly as if the eggs were the eggs ofsea-urchinor starfish in which development customarilytakes place outside the body.

True, this is only the first step, and muchharder ones remain to be taken ; but if wereflect that it is not a century since the natureof fertilization and the mere external appear-ance of the early stages of development wasdiscovered, it will be seen what progressbiology has made.

If ectogenesis were ever possible, we could54


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BIOLOGY AND THE HUMAN INDIVIDUALplay all the tricks we liked on the earlydevelopment of man ; and, as it is onlyduring early development that there is thepossibility of effecting any large alterations inthe fundamental plan of the organism, its im-portance can be seen. For instance, the limitto human brain-power probably lies in thesize of the female pelvis, which cannot givebirth to babies with heads above a certainsize. Abolish this cramping restriction, andyou could embark upon an attempt to en-large the human brain. Furthermore, asHaldane pointed out, ectogenesis would makeit possible to practise an intensityand rapidityof eugenic selection enormously beyond whatcan be done if the human species keeps to itsancestral methods of development ; but thatis another story.Then we must remember that much moreof our growth takes place before birth thanafter. I shall be reminded that we weighabout seven pounds at birth, and perhaps ahundred and fifty at maturity. But growthis essentially a process of self-multiplication,so that the measure of growth is the number

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WHAT DARE I THINK?of times a piece of living substance multipliesitself. And, judged by this criterion, the pre-natal period is vastly more important. Forthe fertilized egg weighs about one-hundredthof a milligram, so that the baby at birth isabout three hundred million times as large aswhen it began its independent career, whileafter birth it will only multiply itself abouttwenty times. Even from the time when thegeneral plan is well established, the multi-plication before birth is round about a milliontimes.Now this is important when we are con-sidering changes of proportion. Changes ofproportion are brought about owing todifferent parts or organs possessing slightlydifferent rates of growth. In just the sameway, two sums of money increasing atdifferent rates of compound interest will becontinually changing their proportionateamounts. The legs, for instance, grow alittle faster than the trunk, the head a littleslower. Ifwe could find a means of alteringthe growth-rate of an organ, even by themerest fraction, during the whole of the pre-

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BIOLOGY AND THE HUMAN INDIVIDUALnatal period, we should make a big differencein the proportions of the resulting body. Weare beginning to understand a little about thefactors controlling the growth of parts rela-tive to each other, and may perhaps beallowed to toy with the idea ofcontrolling theprocess, producing at will stocky and thick-set fellows or leaner types with long legs anda long reach. And this, as well as other in-terferences with normal development, mightwell be possible, even ifwe could not cultivatethe embryo outside the body, by means ofinjections.Such speculations are worth thinking over ;

they seem far less unlikely candidates forrealization within a century than would haveappeared some of the modern applicationsof physico-chemical science, such as beamwireless, or million-volt transformers, orsynthetic dyestuffs, to the physicists andchemists of a hundred years ago. However,there are other possibilities more nearlywithin our grasp, of which it is perhapsmore profitable to speak ; and here we shallsee very clearly the restriction of earlier

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WHAT DARE I THINK?work to the medical side and to the rectifi-cation of defect.Everybody to-day knows of the existence of

the ductless glands. Indeed, the layman'sidea of their powers is often exaggerated.Popular writers on science have been apt tolet their enthusiasm run away with them, andimply that ' glands ' are all-important thatthe construction of the brain counts for muchless in regard to personality than does thebalance of the ductless glands, that they areomnipotent as far as the chemical regulationof the body is concerned, or that changes inthe degree of their activity will account for alarge part of vertebrate evolution.

But, even ifwe discount such one-sidedness,there is no doubt that they are of the greatestsignificance in the life of ourselves and otherbackboned animals. From one aspect theyrepresent what we may call the chemicalskeleton of the animal, each gland producingthe same kind of stuff throughout its evolu-tionary career, whether in fish, frog, bird orhuman being. From another, some of themat least can be looked on as nature's drugs,

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BIOLOGY AND THE HUMAN INDIVIDUALcapable of whipping up the activities ofordinary flesh to otherwise unattainableheights, and yet without evil after-effects.Remove the human thyroid, for instance,and the general chemical activity of the bodyis cut down by about half. The thyroidhormone, as has aptly been said, is to theslow fire of living metabolism what a forceddraught is to a furnace. The adrenal candischarge into the blood a substance whichenergizes the whole organism for emer-gencies. The hormone of the reproductiveorgans can sensitize the brain so that itsactivities are concentrated upon the oppositesex, and all else falls into a secondary place :in some cases even food is forgotten thebull sea-elephant during the rut will go forweeks without once eating.And every ductless gland has importantfunctions to perform. The pituitary controlsobesity, is concerned with gingering upplacidity and sleepiness oftemperament, pro-motes growth of the skeleton, is needed forthe development of thyroid and reproductiveorgans. The thyroid is necessary for the

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WHAT DARE I THINK?development ofnormal brain-power and nor-mal stature, and, in addition to its generalfunction of forced draught, regulates thescale of temperament from sluggish tonervously excitable. The adrenal is con-cerned with the normal course of sexualdevelopment, and is responsible, it appears,for much of the general tone of the bodyas well as for the emergency energizingof which we have already spoken. Thepancreas enables our tissues to utilize carbo-hydrate food ; the parathyroid helps themto utilize lime, and probably keeps growthin check, while its deficiency induces onekind of tetany. The reproductive organsare responsible for the physical and mentaldifferences between the sexes, as well as forthe urge to love.Thus most, and perhaps all of them, exertan effect upon, or perhapswe should say makea contribution to temperament, and many ofthem influence the proportions of the body.

Physique and temperament here are thearcana of individuality. It would be naturalto suppose that biological science would have

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BIOLOGY AND THE HUMAN INDIVIDUALexploited to the full the possibility of controldisclosed by its discoveries concerning theductless glands, and would be capable ofmoulding the individual to its will ; yet thisis very far from being the case. The know-ledge has been used practically, but almostsolely in the medical field. The control prac-tised has been almost exclusively the controlofmarkedly abnormal conditions. Insulin isgiven to correct diabetes : cretins may berestored to normality by thyroid treatment ;grafts and extracts of the reproductive glandshave been used successfully in under-sexedcases and in precocious senility ; para-thyroid helps in certain defective states ofbones or teeth ; and so on and so forth.These uses of our knowledge are important ;they have saved many lives, rescued manypeople from ill-health. Yet the larger fieldremains almost untouched. Various patho-logical extremes of temperament, like thoseof a nervous, pop-eyed sufferer from Graves'Disease or of the Fat Boy in Pickwick, areknown to be due to disturbances of ductlessgland function ; and so are various physio-

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WHAT DARE I THINK?logical extremes of physique, like the long-limbed giant, the heavy-faced and large-handed and large-footed acromegalic, thetype who will put on vast quantities of fleshwhatever his diet (the Fat Boy again), or thePeter Pan type of semi-dwarf who, thoughperfectly proportioned, never grows up fully.

It is further quite certain that differencesof temperament and proportion which fallwithin the normal range are also in largemeasure due to differences in the balance ofthese same glands. What we are pleased tocall the normal, however, includes a greatmany conditions which we regret. Poorgeneral tone, hyper-sensibility, precociousobesity, premature ageing, growth whichwhile stunted or over-lanky can hardly becalled abnormal, undue shortness of armsand legs, unreflective energy and impetuositythat can hardly be called maniac but arealways leading its possessor into awkwardsituations, placidity that oversteps the markand becomes downright and cowlike dullness

there is no doubt that such endowments aremore often than not due to some unusual con-

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BIOLOGY AND THE HUMAN INDIVIDUALdition ofthe ductless glands. Would it not beadmirable ifwe were in a position to remedysuch flaws ? would it not be convenient ifwe were able to adjust our temperamentwithin reason to our circumstances ?Why then has so little been accomplished

in this field ? For one thing, because ourknowledge is so recent. We must not forgetthat almost all the real advances in the studyof the ductless glands date only from thepresent century, though fundamental pioneerwork was accomplished about fifty years ago ;the very word hormone is not thirty years old.Secondly, because in most cases the spur todiscovery has first been applied by medicine :diseased conditions demanded cure, and thecause was found to reside in the defectivenessof this or that gland. But mainly because thesubject is so complex. The earlier work inthis field established the fact that each glandhad some definite function : we could thinkof the thyroid doing this and the pituitarydoing that, in the same clear-cut way, itseemed, as one could think of the craniumprotecting the brain or the heart pumping

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WHAT DARE I THINK?the blood. But later work has shown thatthis picture is a gross over-simplification.Each gland does have a definite main func-tion ; but it can only exert that function byvirtue ofwhat other glands are doing or havepreviously done, and by its own function it isalways modifying the working of its fellow-glands. The system of the ductless glands is,in fact, in a condition of elaborate balance ;it constitutes, as one writer has well put it, aninterlocking directorate.The thyroid will not develop unless the

pituitary is present ; and, even when it isproperly formed, its activity depends in partupon pituitary secretion. In the same waythe reproductive glands need the secretion ofthe adrenal and of the pituitary if they are togrow normally. The pituitary gland consistsof two quite distinct parts ; and in loweranimals, at least, the action of their twosecretions is in certain aspects antagonistic.Excess ofadrenal secretion causes the thyroidto damp down its activities. t The differentglands, in fact, are in a state of delicateequilibrium. The secretion of one stimu-


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BIOLOGY AND THE HUMAN INDIVIDUALlates the activity of a second, depresses thatof a third, is activated by a fourth, and in-hibited by a fifth ; each change which isinduced reverberates by action and reactionthrough the whole system.The complexity of this arrangement hasonly fully dawned upon physiology in thelast ten or fifteen years ; several decades ofhard work and patient exploration mustelapse before the invisible machinery, thelevers, springs, compensations and adjust-ments of this balanced system are fully under-stood. And we must set ourselves also tounderstand its variations. It is easy to seehow a gross defect in one of its memberswill call forth serious symptoms, as when thepancreas is overworked, or the thyroid failscongenitally to develop. But, in a partner-ship so nicely adjusted and balanced, it is atthe moment hard to understand just whatunderlies those quantitative alterations whoseeffects on temperament and physique remainwithin the bounds of the normal. Thenormal thyroid, for instance, has astonishingpowers of adjusting its size and its activities

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WHAT DARE I THINK?to the calls upon it ; what then determinesthat some people strike a balance with aslight over-activity of thyroid, others with aslight under-activity ?But it must be possible to find answers

to these questions ; and once the answershave been found, hitherto undreamt-of possi-bilities open out of control over the veryessence of our selves, over both physical andmental aspects of our organism.The same sort of possibilities lie before thestudy of drugs. They, too, have in the pastbeen used mainly for therapeutic purposes,to remedy definite defects of working in thebodily machine to spur a flagging heart, tokill the germs of this or that disease, to stopbleeding, to induce anaesthesia, to promotethe muscular contraction of the uterus inlabour, to dull over-excited nerves, and so on.But, with rare exceptions, such as caffeineand alcohol, nicotine and cocaine, they findno place in everyday life ; and of those whichare so used, many are definitely harmful, andthe rest can easily be abused.Meanwhile the explorations of pharmaco-

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BIOLOGY AND THE HUMAN INDIVIDUALlogy are discovering many remarkable effectsofchemical substances. Out ofcoal the phar-macologist can prepare acetanilide which willbring down the temperature ; with othersubstances he can send the temperature up.Out of raw liver he gets a substance whichwill build blood ; out of a Mexican cactushe can extract a drug which will promotethe strength of visual imagery in thinkingand will make some people hallucinate ; hecan manufacture out of ordinary materials inhis laboratory the thyroxin with which thethyroid gland stimulates the body to newactivity ; he can reduce or increase the bloodpressure at will. But, again, the results havebeen applied almost solely to set right some-thing which has gone wrong, not to opennew doors.The fact seems to be that most of us are

loath to consider this possibility of openingnew doors, for the reason that those drugswhich are now used deliberately for that pur-pose, like opium, alcohol or cocaine, are soreadily abused. It seems a new garden on towhich their doors open ; but it has a way of


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WHAT DARE I THINK?turning into a prison. On the other hand,the very existence of the ductless glandsreminds us that nature is drugging us everyday without ill effects. A man whose thyroidhas become defective must take a perfectlydefinite amount of thyroid extract every dayifhe is to remain in health : too little, and hestill is sluggish in mind and body too much,and he becomes thin and excitable. Hecannot dispense with jt any more than he candispense with food ; but, whereas normallyhe should make it for himself, now he has tobe provided with it from the outside. And,again, as with food, both too much and toolittle are harmful.

It should not be impossible to work out acombination of pharmacological substances,each in the right amount and right propor-tion, which would be capable of toning up aman's faculties by say ten per cent., and yethaving no bad after-effect, other than whatis already exerted by our nervous, rushingmodern lives. It would be somewhat differ-ent according to the kind ofwork which wasneeded hard physical labour like that of a

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BIOLOGY AND THE HUMAN INDIVIDUALminer, unremitting activity of various sortslike that of a cabinet minister, routine likethat of a civil servant, pure brain-work likethat of a mathematician ; and as our know-ledge is increased, the prescription couldbe adjusted to individual physique andtemperament.At the end of Jules Romains 5 play, DrKnock, the doctor expatiates on the glorieshe has achieved for medicine, by persuadingvast numbers of perfectly well people thatthey are ill. With a wave of his hand, hereminds his hearers that at this very moment,within sight of his house, five thousandgullets are swallowing their evening potion,and in a moment five thousand temperatureswill be taken. It would be an even greatertriumph for medicine if it could invent some-thing which would make the average wellman feel better, and persuade the populationat large to adopt it, so that not thousandsbut millions would simultaneously be takingtheir c little daily dose/And then there is the psychological side ofbiology. Pure human psychology is at the

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WHAT DARE I THINK?moment a somewhat isolated and esotericscience. But it cannot long stay in this posi-tion. Accurate studies on the brain, such asthose of the great Pavlov, are linking it withnerve-physiology. Work such as that ofKretschmer and Draper is joining it up withgeneral physiology and is emphasizing fromanother angle the unity of mind and matterwithin the single organism. The vast amountofrecent work on animal behaviour which atlast of late years has paid serious attentionto the monkeys and apes as well as to cats,pigeons, frogs, ants and worms, is providingthe proper evolutionary background ; by sodoing, if it may rob human psychology ofsome of its more romantic speculations, itwill force it into biological sanity.Already many new possibilities are open-

ing up. There is the possibility that we maybe able to bring children up without thedeformation of fear, the friction and wasteengendered by repression, the abnormal pre-occupation with sex, which have in the pasthindered the free use of the energy ofhumanminds. We are just beginning to see that the

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BIOLOGY AND THE HUMAN INDIVIDUALrule-of-thumb methods of our ancestorsmight be replaced by a scientific cultivationof the mind, the one as different from theother as is modern scientific agriculture fromthe shifting cultivation of a primitive tribe.We can see the possibility ; but as yetwe can hardly envisage the result. Whatchanges in conditions of work would bedemanded by a population bursting withmental energy ? What alterations in mar-riage and sexual relations in general wouldresult from an uninhibited mental attitudetowards sex ? What would be the result uponour political system of an all-round enlarge-ment of rationality and freedom ?

It is impossible to say ; but it is clear thatthe most exciting and, indeed, disturbingpossibilities loom up before a civilizationequipped with the psychological knowledgewhich will inevitably have been gained beforethe end of the present century the possi-bility of training the mental organism in newforms, and of tapping new supplies of mentalenergy in the life of the population as a whole.* # * * * *

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WHAT DARE I THINK ?I might have multiplied examples, espe-

cially from medicine ; I might have spokenof the very real possibilities of prolonging life

so-called c rejuvenation ' opened up byvarious operations on ductless glands. ButI have, I hope, said enough for my purpose.My purpose was simply this : to show thatbiology is entering upon the phase begun byphysico-chemical science about a centuryago, where knowledge can be translated on alarge scale into practical control. This newpractical control will in many respects havemore fundamental effects than the old, sinceit will be exerting its influence not on thenature around man, but upon man himself.The prospect is disturbing, in some waysperhaps even alarming. But that is all themore reason for facing it in time and in theright spirit. There will be no preventing itscoming, no possibility of holding back thetide. But we can prevent its advance beingpiecemeal and haphazard, and can use ourimaginations ahead of the event. The diffi-culty with the applications of science hasoften been that they acquire a momentum of

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BIOLOGY AND THE HUMAN INDIVIDUALtheir own and take charge of events. SamuelButler envisaged industrial humanity as theservants, slaves or parasites of the machineswhich represent the latest dominant type ofexistence brought forth by evolution ; andthere is something in what he said. Man asscientist can provide practical control ofphenomena. It is for man as man to controlthat control.

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CHAPTER IIIMan and his Heredity

A7 the instant of our conception, we aredealt the hand of cards with which wehave, willy-nilly, to play the game of life ;what hand we shall get at this inevitablemoment is almost as much a matter of merechance as it is each of the trivial times whenwe pick up the thirteen bits of pasteboardfrom the green baize of the card table. Thatis one of the twentieth-century discoveries ofbiology ; if you prefer, it is an amplificationof what was in some measure known before.But the amplification is so radical that itdoes really constitute a new discovery ; forit substitutes for the vague guesses of earliergenerations the picture of a precise andorderly mechanism, for loose and generalideas a detailed and accurate scientific theory.It is no exaggeration to say that in the thirty


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MAN AND HIS HEREDITYyears of the present century heredity hasrisen from one of the vaguest and most back-ward of the biological subsciences to becomethe discipline in which biology most nearlyapproximates to the type of physics, patternof the natural sciences, in which induction,theory, deduction and experimental testingplay equal and complementary roles in anindivisible and rapidly advancing whole.

Let us return to that moment of destinywhen our inheritance is decided. How fan-tastic is the scene of the microscopic drama,how alien from the ideas of other ages theideas which it paints on the background ofour thought ! There is no generation of lifeby the masculine principle in a mere soil pro-vided by the female ; there is no breathingin of wholly new life from supernatural or,indeed, any external agency. It is not themother's blood which decides the tempera-ment and capacities of the child, nor what sheand still less the father have eaten, drunk,experienced or thought about. There is acontinuity of life and living matter both fromthe father and the mother to the offspring :

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WHAT DARE I THINK?two fragments of living matter, which havedetached themselves from the parentalbodies, unite to form the one fragment whichwill grow into the body of the child ; andthe child's qualities are determined, in so faras heredity has its say in the matter, by theparticular assortment ofchemical units whichit receives at this instant.One inert spherical piece of living matter,

somewhere about a hundredth of a cubicmillimetre in bulk, just visible under a hand-lens, has been squirted by hydraulic pressureout of the water-cushion in which it hasgrown to maturity in the little pinkish wartyovary. Wrapped round by the frilled trum-pet mouth of the tube which leads from thecentral cavity of the body to the outer world,it is forced downwards into the dark andcorrugated recesses of the duct. There, be-cause two human beings, a man and a woman,have been led by love or driven by lust, itfinds itself in the presence of some membersof a huge population, as great as the entirehuman population of London or New York,of strange and altogether microscopic crea-


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MAN AND HIS HEREDITYtures, the sperms, which resemble miniature,more active, but less intelligent tadpoleslashing their tails, being swirled blindlyhither and thither by the currents all butimperceptible to us, violent to them whichthe tube engenders in the fluid cavity bymeans o

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