DESIGN IN NATUEE 255 



garnous trees are known first in the carboniferous 

 period ; mammals in the lower Jurassic ; birds in 

 the upper Jurassic ; the Primates and primitive 

 hoofed mammals in the lower eocene ; grasses in 

 the oligocene, Euminants in the miocene, and man 

 in the pliocene. The mesozoic mammals were all 

 quite small, and we do not know the structure of 

 their feet, so we cannot say whether they were 

 arboreal or not; but, with this possible exception, 

 we find that the different classes came into existence 

 just when they were wanted. 



We must remember that these groups of plants and 

 animals form widely separated branches of the tree of 

 life, and that the necessary correlations, of which I 

 have been speaking, lie outside the jurisdiction of 

 natural selection; which, although it regulates the 

 development of each branch, has no power of co- 

 ordination between two branches, unless one forms 

 the food for the other. So that there is no reason 

 at all why they should have been developed in the 

 particular order in which they appear. 



For example, the origin of birds depends chiefly on 

 the development of highly complex papillse in the 

 skin, from which the feathers are formed. If these 

 had not been developed in the naked skin of a reptile, 

 flying birds would never have come into existence. 

 And if there had been no birds, or even if their origin 

 had been delayed until the miocene period, there 

 would have been no monkeys nor man. So also, if 

 no Euminants had been developed, this would not 

 have prevented the appearance of apes or even of 

 man ; but man would have remained in the stage of a 



