48 THE THEORY OF EVOLUTION 



of cases the resemblances of this kind are very super- 

 ficial and can be easily explained by the process of 

 adaptation to functions common to both/ l 



Conclusions derived from palaeontology : 



We have seen that the changes or transformations 

 which are experienced by the organisms never exceed 

 the limits of the families and classes, nor generally 

 those of the orders ( 2). 



According, therefore, to the present position of science, 

 there is no unlimited transformation in the animal world. 



It is true that with the Vertebrates, on the whole, 

 the higher classes appear after the lower ( 1). To 

 show how both, viz. the appearance after each other 

 and yet no derivation from each other, can be brought 

 into accord is reserved for the evolutionary hypotheses. 

 We will express a supposition relative thereto later on. 



In 3 we saw in what way originally like or similar 

 forms could arrive at varied appearances. This happens 

 through an ever-increased adaptation to quite definite 

 modes of life by which, in some cases, the whole organ- 

 ism is transformed generally, however, only separate 

 organs. There is often observed also an increase of 

 size, in conformity with a recognized law, mostly in 

 conjunction with other changes, but in a few there 

 is increase of size alone. 



It may also happen that animals originally widely 

 separated in kind become more similar by variation 

 in the same direction. 



1 Deperet-Wegner : Die, Umbildung der Tierwell, p. 213. 



