WORMS AND CCELENTERATA 265 



preserved quite unaltered. The maw - worms, for 

 instance, have many adaptations that they have 

 acquired since that time in the course of the earth's 

 development, and we do not know if they had not at 

 that time adaptations that they have since lost. Thus 

 we cannot form any absolutely safe picture of the 

 primitive worms that became, in certain circumstances, 

 the ancestors of the vertebrates. We can only say that 

 they had the worm-type ; that their principal organs 

 had, in general, a structure and arrangement more 

 closely resembling that of the worms than any other 

 living animals. 



Thus the statement that "man descends from fishes" 

 does not mean that w r e have ancestors who resembled 

 any of the actual fishes, but that at a certain period they 

 were gill-breathing, aquatic animals with a structure to 

 which the nearest approach is found among the fishes of 

 all actual animals. So, again, man does not descend 

 from the apes, as is often said, but from beings that 

 must probably have resembled the actual apes more than 

 man. The apes have not been fixed in their organisation ; 

 they have diverged steadily from their ancestors by 

 constantly acquiring new adaptations. Their ancestors 

 were probably brothers of man's ancestors, but that does 

 not justify the above statement. On the strength of 

 this probability we may, at the most, say that man and 

 the ape have a common ancestor. 1 



1 There are scientists who do not admit that man had ape-like 

 ancestors. They believe that the apes are no more clearly related to 

 man than the ruminants or carnivores, or, especially, the kangaroos. 

 This view, however, has few supporters, and its arguments are not at 

 all convincing. 



