184 GENERAL DISCUSSION [ch. xiv 



the early stages of non-adaptive characters is considered, and it 

 is pointed out that by differentiation there need not be such 

 stages, nor is adaptation called in. In case xii (p. 118) is con- 

 sidered the case of alternate and opposite leaves, a very common 

 case of divergent characters with no transitions, and where it 

 is almost impossible to suggest any adaptational value in the 

 difference between them. Selectionists have to admit that 

 anatomical needs are more potent than adaptational. This ques- 

 tion of the relative value of characters has been somewhat 

 ignored. In case xiii (p. 120) staminal characters are dealt with 

 in the same way, and give similar evidence. In case xiv (p. 122), 

 the berry is dealt with, and incidentally it is shown that there is 

 little evidence of adaptation in this phenomenon, so often quoted 

 as an illustration of it. Case xv (p. 124) deals primarily with 

 achenes and follicles. Natural selection could not produce these 

 in their perfect form, nor could it produce the perfect pod, and 

 distinguish between this and the follicle in the marked way that 

 one always finds. In cases xvi, xvii and xviii various other 

 structural puzzles are considered, all much more easily explained 

 by differentiation. In case xix (p. 129) the puzzle of correlated 

 characters in so many of what are usually called adaptations is 

 discussed, and it is shown that while it is quite inexplicable by 

 natural selection, it is somewhat more easy with differentiation, 

 which does not demand an adaptational value in everything. 

 These (adaptation) correlations are useful, while most are not, 

 but some day, perhaps, cytology will bring us the explanation of 

 correlation phenomena. 



In chap. XII some further tests are considered under the head 

 of Taxonomy, though largely a continuation of the last. The 

 position of the largest genera of a family is dealt with in case xx 

 (p. 134). On the theory of natural selection one can make no 

 prediction about them, but on that of divergent mutation it is 

 clear that in general they will be widely separated, inasmuch as 

 they will have inherited their characters from the earliest muta- 

 tions that took place in the family. This is just what proves in 

 general to be the case, as is illustrated by the cases of the Ranun- 

 culaceae and the sub-family Silenoideae, etc. In some cases, e.g. 

 Clematis, the second largest genus in its family, the genus does 

 not seem to have given rise to a sub-famih' inheriting its most 

 obvious divergent character, the opposite leaves, but more usually 

 this is the case, and one finds the large genera heading sub- 

 families or other divisions. This is as predicted, whilst natural 



