CORRESPONDENCE 



To THE Editor of " Science Progress " 



THE INHERITANCE OF ACQUIRED CHARACTERS 



I. From Julian S. Huxley, M.A. 



Sir, — The article by Prof. MacBride on " The Inheritance of Acquired 

 Characters," which appeared in Science Progress for January, contains 

 certain statements which I think should not pass unchallenged. As regards 

 the positive results of experiments on the transmissibility of modifications, 

 the matter can be allowed to rest until further independent work has either 

 proved or disproved their accuracy. The issues hanging on them are so large 

 that they cannot be accepted as gospel on the word of a single investigator, 

 however capable. 



It is with other aspects of Prof. MacBride's position that I am con- 

 cerned. On p. 309 he states that " the pathological mutants which Mendelians 

 employ for their experiments are utterly unhke the variations which the 

 study of comparative anatomy induces us to postulate as the material of 

 evolution " (italics mine). Such a statement is not only inaccurate ; it is 

 unfair. Among the characters which are known to segregate according to 

 Mendelian laws are the finest gradations of coat-colour and marking in rodents 

 (e.g. mice, guinea-pigs) ; size (fowls, Punnett ; peas, Mendel) ; the forms of 

 pistil and stamens in heterostylic plants ; every shade of eye-colour in 

 Drosophila ; starchiness and sugariness of seeds (peas, maize) ; leaf-form 

 (many plants) ; phototropism and its absence (Drosophila) ; sex (many 

 animals and plants) ; hen-feathering (fowls) ; minute modifications of 

 proportion and distribution (Morgan's modifying genes) ; increases or 

 decreases of vigour (maize. East and Jones) ; probably the patterns of 

 dimorphic butterflies ; probably many apparently quantitative characters, 

 such as flower-size (tobacco-plant. East) ; fertility (fowls. Pearl ; Drosophila, 

 Hyde) ; fluctuation of pattern (rat, Castle) — but the list could be extended 

 indefinitely. I have jotted down the first instances that came into my head 

 of characters that happened to be both Mendelian in their inheritance and 

 normal in their nature. 



It is natural that a great many abnormalities are also known to be 

 inherited according to the same laws ; they are what strike the eye of the 

 investigator first. But it is not only in Genetics that pathology has helped 

 to an understanding of physiology. 



It is, in any case, quite obvious that the mechanism of segregation is a 

 fundamental part of the organisation of animals and plants. It may or may 

 not turn out to be identical with the chromosome-mechanism ; but, in any 

 event, I do not believe that there exists a single geneticist to-day who would 

 deny that it represented something universal and fundamental. If so, it 

 is obvious that it will be capable of segregating the abnormal equally with 

 the normal. Prof. MacBride, in order to clear the ground for theories 

 which do not fit in well with Mendelism, prefers to look at the abnormal. 

 Most zoologists will, I think, prefer to look at the normal. The mechanism 



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