CORRESPONDENCE 301 



was this, that the slow, continuous change in the chromatin has been the 

 dominating factor in evolution, and that the sudden mutations with which 

 the Mendelians have chiefly experimented have not been the kind of changes 

 which have led to the production of new species of animals, and in this opinion 

 the best systematists whom I have consulted agree with me. An eminent 

 icthyologist thus phrased it : " Mendelism is all right, but it has got nothing to 

 do with evolution." 



Taking now the points which Mr. Huxley raises in order : 



1. He complains that I asserted that the mutations experimented with by 

 Mendelians are pathological, and that I had not attempted to defend this 

 statement. 



I am certainly not prepared to assert categorically and dogmatically that 

 every mutation which has been the subject of Mendelian experiment is 

 pathological. Such an assertion could only be justified by a detailed 

 examination of each case, but I reassert that the overwhelming majority of 

 them are pathological, and that the language in which Mr. Huxley brings 

 forward his so-called exceptions is so chosen as to obscure this fact. To 

 give one instance, he mentions " size " as a quality which is certainly not 

 pathological, but which is inherited in a Mendelian manner. Now allied 

 species certainly do differ in size, and a slow, continuous increase in size is 

 often the accompaniment of the evolutionary series which we find in fossils ; 

 but there is all the world of difference between cases like these and the real 

 Mendelian mutants like the dwarf OEnothera, which are as genuinely patho- 

 logical as are human dwarfs. 



2. Mr. Huxley is good enough to refer me to a discussion by Miiller on 

 differences of eye-colour between allied species, which appear to be most 

 easily interpreted on the factorial hypothesis. I need no instruction from 

 either Mr. Huxley or Miiller as to the interpretation to be placed on these 

 differences, nor am I, nor, as I believe, are the majority of zoologists to be 

 influenced by the arguments of Mendelians who are determined to crush 

 everything into a Mendelian mould. Certainly the attempts to deal with the 

 differences between human races in respect of eye-colour on the Mendelian 

 basis have not been conspicuously successful. The so-called duplex eyes 

 which contain brown as well as blue pigment show every gradation from the 

 heavil}'^ pigmented eyes of the Negroes and of the Mediterranean races to 

 cases — equally ranked as duplex — where traces of brown pigment are only 

 to be discovered by a magnifying lens. If two blue-eyed parents give rise 

 to blue-eyed children, then Mendelians assert they are simplex — if they happen 

 to have a brown-eyed child then they had concealed brown pigment. This 

 is the kind of arguing in a circle to which I referred in my last letter, and to 

 which I strongly object. 



3. Mr. Huxley reasserts that when two allied strains differing in size 

 are crossed there is segregation in F.2 Against this I can only reiterate that 

 the result of both Bateson's and Punnet's experiments is, that when a large 

 strain and a small strain are crossed, though individuals of varying size are 

 produced in F.2, the large strain is never recovered. 



4. With regard to coat-colour in Mammals, I asserted that the colour 

 differences between allied species were totally dissimilar to those exhibited 

 by Mendelian mutants. In pity for my ignorance Mr. Huxley is good enough 

 to refer me to a book entitled. The Growth of Groups, by Dr. Lloyd, for proof 

 to the contrary. It is indeed kind of Mr. Huxley to call my attention to a 

 work which has been on my book-shelves for eight years, and which it was my 

 duty to review when it first appeared. This work contains the attempt of 

 an amateur biologist, a member of the Indian Medical Service, to solve the 

 problem of species on the basis of a large collection of rats made in India. 

 No experiments were attempted and no new principle emerged. That 

 amongst a large collection sporadic appearances of mutants occurred is cer- 



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