226 



TEE GENESIS OF SPECIES. 



[CHAP. 



In sucn creatures we see that, from time to time, one of 

 the segments of the body gradually becomes modified till it 

 assumes the condition of a head and this remarkable phe- 



AN ATtNTELID DIVIDING 8PONTANEOTT8LT. 



(A new head having been formed toward the hinder end of the body of the parent.) 



nomenon is repeated again and again, the body of the worm 

 thus multiplying serially into new individuals which succes- 

 sively detach themselves from the older portion. The 

 development of such a mode of reproduction by " Natural 

 Selection" seems not less inexplicable than does its contin- 

 ued performance through the aid of " pangenesis." For 

 how can gemmules attach themselves to others to which 

 they do not normally or generally succeed ? Scarcely less 



