Hormones and Heredity by J. T. Cunningham
page 27 of 228 (11%)
page 27 of 228 (11%)
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known utility whatever, so that the problem presented by these characters
was not explained by any theory of the origin of adaptations. Mendelism, since 1900, has studied experimentally the transmission of definite characters, and maintains that the characters of species are of the same nature as the characters which segregate in Mendelian experiments. Such characters are not in any way related to external conditions, and cannot, therefore, be adaptive except by accident. Professor Bateson goes so far as to admit that such large variations or mutations offer more definite material to selection than minute variations too small to make any important difference in survival, but as regards species the important factor is the occurrence of mutations which are inherited and at once form a distinct definite difference between allied species which is not due to selection and has nothing to do with adaptation. In a book entitled _Problems of Genetics_, 1913, Bateson describes several particular cases which show how impossible it is to find any relation at all between the diagnostic characters of certain species or local forms and their mode of life. One of these cases is that of the species of _Colaptes_, a genus of Woodpeckers in North America, of which a detailed study was published in the _Bull. Am. Mus. Nat. Hist._, 1892. The two forms specially considered are named _C. auratus_ and _C. cafer_, and they differ in the following seven characters:-- _C. auratus._ _C. cafer._ 1. Quills yellow. 1. Quills red. |
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