CORRESPONDENCE 455 



and Johannsen take the step of denying its existence. If the facts refuse 

 to fit into tlieir scheme, so much the worse for the facts. 



It is perfectly true that it is difficult, and often impossible, to show how 

 the distinctions between two allied species are related to function. This is 

 because — to steal Mr. Huxley's fire — the activities of animals are " balanced 

 reactions," and, until we succeed in analysing the physiology of animals, 

 much better than we have done, we cannot hope to show why the alteration 

 of one function influences others. We do not know why, when our race 

 migrates to Australia, their children tend to give rise to taller men — it cer- 

 tainly is not a case of natural selection nor chance transportation of particular 

 genes to that continent. 



Having constructed the imaginary edifice of genes, the next step would 

 be to show how it functions in producing adult structure. From taking this 

 step Morgan wisely abstains, but where he fears to tread Huxley rushes in. 

 In answer to my query as to how the cells of the abdomen of a frog tadpole 

 acquired the capacity of forming lenses, he states that all the cells of the 

 body have this power because all the nuclei of the body possess the whole 

 gene-complex — or, as I would put it, all the potentialities of the species. In 

 this assumption I agree with Mr. Huxley — he will find it concisely stated in 

 my textbook of Embryology, published seven years ago, but it involves the 

 entire giving up of the Weismannian distinction between germ-plasm and 

 somato-plasm. But when Mr. Huxley goes on to state that this assumption 

 renders it easy to understand the building up of the adult body, and processes 

 like regeneration and reproduction, one is driven to ask whether he imagines 

 himself to be throwing any light on the problems which he discusses. The 

 gene-complex " reacts " differently to different media, and so in one place 

 a head is produced, and in another a tail. Regeneration is of the same 

 character as the completion of a truncated crystal ! ! Really, Mr. Huxley 

 might be invited to restudy the works of Driesch. Does he forget that the 

 supposed different media to which the gene-complex reacts are created 

 by itself, or that the growth of a crystal is due to the monotonous linking 

 together of the same kind of atoms ? 



The cytoplasm of the young Nematode egg is indifierent material ; as it 

 ripens it has an elaborate organisation bestowed on it by emissions from the 

 nucleus, so that different cytoplasmic substances are arranged in definite 

 relations to one another. To what different media has the gene-complex 

 " reacted '\in this case — and is the phrase " reaction to stimulus " a physico- 

 chemical conception at all ? 



In conclusion, I should like to comment particularly on two paragraphs 

 of Mr. Huxley's article. He presumes to judge of the mental prejudices 

 which prevent his opponents from accepting the views of Morgan, and sug- 

 gests it is because they dislike the idea of chance variations as the raw 

 material of evolution, and " refuse to accept the universe." I pass over the 

 questionable taste of a young and comparatively untried biologist like Mr. 

 Huxley attributing motives to senior biologists, amongst whom must be 

 reckoned the distinguished botanist Sir Francis Darwdn — who made the 

 inheritance of acquired characters the subject of his presidential address 

 to the British Association at its Dublin meeting in 1908. I beg to assure 

 him that it is not because they have prejudices that his opponents fail to 

 agree with him : it is because they know considerably more of the universe 

 than he does, and find the Morgan-hypothesis inconsistent with the facts. 



Then, in the opening sentences of his essay, he indicates that he is putting 

 forward a new theory, and trusts to time to enable it to gain the victory over 

 the older one. Nothing could be a more complete travesty of the facts. I 

 well remember the enthusiasm with which the Mendelian theory was received, 

 when it was introduced to the scientific world in the early years of this century. 

 We thought that at last the key to evolution had been discovered. As a 



