130 TEST CASES [ch. xi 



great variety of conditions in which the large families now live 

 must have been due to subsequent adaptation. But this leads to 

 the somewhat surprising conclusion that adaptation must have 

 been very strongly in evidence in early days, with a corresponding 

 amount of destruction to separate the families, for which we have 

 no evidence. 



Or why were one-fifth of the flowering plants picked out to 

 have only one seed-leaf instead of two, to have the parts of the 

 flower in threes instead of in fives, to have leaves with parallel 

 veins instead of netted, and to have so different an internal 

 anatomy, with no simple process of growth in thickness? And 

 still more difficult is it to explain, on the theory of gradual 

 selection, why all these characters should go together, when they 

 have no adaptational meaning, either singly or in combination. 

 One can conceive that the anatomy of the Monocotyledons was 

 definitelv disadvantao^eous, which mav explain whv there are 

 comparatively few trees among them; yet the palms seem 

 successful enough, or the bamboos. But the important fact 

 remains unexplained, and not to be explained upon the theory of 

 gradual selection, that, as already pointed out, the Monocoty- 

 ledons maintain their proportion of one in five in all important 

 parts of the world. 



An interesting case of correlation incidentally showing the 

 totally useless nature of many, or nearly all, of the generic and 

 specific characters may be seen in the genus Pyrenacantha in 

 Icacinaceae, which has a drupe with the inner side of the shell 

 thorny; correlated with this are definite holes right through the 

 endosperm to leave room for the spines. Here is a case that it 

 would puzzle the selectionist to explain, and there are many more. 

 And it is somewhat difficult to imagine intermediate stages. 



To try to explain these correlations in terms of gradual adapta- 

 tion is a practical impossibility, and if they were formed at one 

 step, how does adaptation come in? Take, for example, the case 

 of climbing plants, already considered (p. 57). Or take parasites, 

 which must also have been a later development than non- 

 parasitic plants. Until the sucker has actually penetrated the 

 host, the habit will be of no value, so how did it begin under the 

 operations of natural selection with gradual adaptation? And 

 incidentally, such parasites as the fungi live almost entirely 

 within the host, where the conditions must be more or less the 

 same for all, so how did they come to develop such numbers of 

 species with definite structural diff'erences? How did the ordinary 



