IV. 
The Origin of Specific Forms 
of Life. 
HE origin of species in the 
A animal kingdom p r e s e n t s 
another difficult problem. In the 
animal kingdom, as in the vege¬ 
table, we find quite distinct classes, 
orders, families, genera and 
species. Evolution seeks so to re¬ 
late all these as to prove that they 
have a common origin, that all liv¬ 
ing forms have been derived 
through a process of gradual modi¬ 
fication by natural selection or 
otherwise, from one or a few simple 
forms of animal life. For confirma¬ 
tion of this hypothesis appeal is 
made to morphology, embryology, 
35 
