more complicated since it now embraces sixteen or seven- 

 teen different problems, each of which in turn gives rise to 

 many subordinate problems. 



The discussion which the author inaugurates re- 

 garding the domain to which the question of 

 Descent belongs, is very well-timed. He forcibly and 

 definitely discountenances the method which transfers 

 it to the domain of religion. The question must be decided 

 by the naturalists themselves according to the strict induc- 

 tive method; that is, the solution must be based on well as- 

 certained facts, without resorting to conclusions deduced 

 from general principles. "Exact research must show that 

 living organisms actually have overstepped the bounds 

 defining their species, and not merely that they conceiv- 

 ably may have done so." Hence it is absolutely necessary 

 to procure the intermediary forms. This is the foundation 

 on which Fleischmann builds and against which no oppo- 

 nent can prevail. Fleischmann first discusses the differ- 

 ences between the classes of vertebrates; the mammals, 

 birds, reptiles, amphibians and fish. For if the differences of 

 their bodily structure could be shown to be one of degree 

 and not radical, it could be supposed that the lines of de- 

 marcation which now delimitate the largertypes might some 

 day vanish. A single illustration suffices for Fleischmann's 

 purpose, viz., the plan of structure of the limbs of the differ- 

 ent classes of vertebrates. The four higher classes are charac- 

 terized by a common underlying plan of limb structure, 

 whilst fish have one peculiar to themselves. On the other 

 hand it is an inevitable postulate of the doctrine of Descent 



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