452 SCIENCE PROGRESS 



the same part of the chromosome as the gene for albinism. The vastly 

 simpler and infinitely more probable supposition is that these mutants 

 represent lesser degrees of damage to the chromosome of the same kind as 

 that represented by the change which produces albinism. It is these minor 

 degrees of damage which are relied on by Mr. Huxley to bring us back to 

 the Neo-Darwinian position — that is, the view that evolution is based on the 

 occurrence of minute inheritable changes in all directions — of which natural 

 selection ensures that only the useful survive. I, too, believe that evolution 

 is based on the selection of small variations ; but these variations are of the 

 nature of the expansion and diminution of function, selection, in fact, of 

 vigorous individuals, which react well, and rejection of weakly individuals, 

 which fail to react. These differences are totally dissimilar, not only in 

 amount, but in nature to the mutants of Drosophila. This even Mr. Huxley 

 admits, when he says that " the alterations of a gene bear no relation to any 

 Lamarckian change." 



The overwhelming majority of mutations which can be crossed with the 

 type, and show Mendelian inheritance, are of the recessive degenerative 

 nature. So markedly is this the case that Bateson, in 1914, suggested that 

 all evolution had consisted in the "dropping of factors," and that all the 

 qualities of Shakespeare were implicit in the original Amoeba, with which 

 animal life began. This, to my mind is the final reductio ad absurdum of the 

 whole theory that evolution has been accomplished by the agency of Mendelian 

 mutations. 



It may, however, be answered that there are some few mutations which, 

 when crossed with the type, are dominant. This is true, but the odd thing 

 is that even in these cases the mutation is of a monstrous character. This is 

 obvious in the case of certain dominant mutations which turn up in man, 

 such as brachydactyly and premature and excessive sloughing of the epi- 

 dermis ; but, even in the case of the combs of fowls, it can be shown to be 

 highly probable. The original shape of comb, with a single serrated edge, is 

 found in the wild bird, and is the only form of comb that is found in any 

 species of Gallus — which is the only genus of birds which possess combs. 

 The combs of domesticated breeds show various degrees of aberration from 

 this ; the lesser degrees of aberration, such as the rose-comb, do not obviously 

 appear to be pathological, but the series culminates in the Polish fowl, in 

 which the comb is replaced by a tuft of feathers seated on a protuberance of 

 the skin, beneath which is a huge vacuity in the skull exposing the brain. 



The most plausible explanation of the dominant mutations would seem 

 to be that they are due to morbid exaggerations of processes which in the 

 type are regulated and kept in check ; but that, in order that this check shall 

 be effective in any given individual, it is necessary that both sides of the 

 house should be normal ; that in the hybrid produced by crossing the mutant 

 with the type the check exercised by the maternal or paternal side alone is 

 not sufficiently powerful to regulate the process. 



But, Mr. Huxley assures us, the pupils of Prof. Morgan have shown that 

 some of the mutants of Drosophila resemble the type in other species of 

 Drosophila. I have no doubt that they have done so, and, in case Mr. Huxley 

 requires other instances, I will supply them. The fur of the albino rabbit 

 resembles in colour the fur of the ermine, and is sold as such to our unso- 

 phisticated factory-girls. Again, there is an albino variety of the axolotl 

 which is of the same pale flesh colour as the cave-newt Proteus. At first sight 

 these resemblances appear to afford a clue to the manner in which the loss of 

 colour took place in the ermine and in the cave-newt ; the expert, however, 

 knows otherwise. The lady who buys her ermine muff is careful to look 

 for the yellowish tinge, which indicates the last trace of the colour which the 

 ermine wears in summer. If the albino axolotl be exposed to light on a light 

 background some slight traces of pigment are developed, but the Proteus 



