CH. XI] B. MORPHOLOGICAL 115 



For that matter, how is it that all the leaves upon a plant 

 match one another so closely as they do, or all the flowers? The 

 only explanation that the supporters of natural selection can 

 give is that morphological considerations are more important in 

 evolution than is natural selection (cf. pp. 120, 121). But how did 

 natural selection begin to develop different types of leaf, and 

 to make them so constant in size and form, and to put different 

 types upon closely allied species (cf. the Thalictrums on p. 104)? 

 There is not the faintest reason to suppose that evolution worked 

 by different rules at different stages in its history, but the selec- 

 tionists seem to think that if by aid of assumptions and supple- 

 mentary hypotheses they can produce some kind of explanation 

 of the phenomena seen at the present day, the past can take care 

 of itself. What we are contending for is that morphological and 

 anatomical considerations are more important than natural selec- 

 tion, and that the latter has not been, unless to some small extent 

 or in some recondite way, responsible for the appearance of 

 important structural characters. It acts upon what is given to it 

 by the process of evolution, which goes on regardless of whether 

 its products are acceptable or not. If they are killed out by 

 natural selection, that is the end of that line, but others will 

 appear. The simple and easy explanation of the phenomena of 

 morphology is that they are due to mutations, which as a general 

 rule probably produce a new form at one operation. To some 

 extent at any rate, there is probably some definite factor in the 

 parent, perhaps some arrangement or structure of the chromo- 

 somes, that determines what will appear in the offspring (and 

 here again perhaps only in certain conditions, as for example 

 possibly under the influence of cosmic rays). But w^e are as yet 

 too completely ignorant of the whole subject to be able to hazard 

 any definite opinion. 



This test evidently gives very strong evidence in favour of the 

 large mutations that are required by the theory of differentiation. 



TEST CASE XI. THE EARLY STAGES 

 OF CHARACTERS 



One of the great difficulties that have always dogged the path of 

 the supporter of natural selection as a cause of evolution, is to 

 explain the beginnings of the various structural characters. This 

 is a problem with which he has had little or no success. We have 

 instanced many of the characters that divide species, genera, and 



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