256 



THE EVOLUTION OF SEX. 



has been sacrificed in reproduction. "The death is an 

 altogether inevitable consequence of the reproduction." 



Nor is this sacrifice confined to the incipient multicellular 

 organisms. Thus in some species of the annelid Folygordius, 

 the mature females break up and die in liberating their ova. 

 This is approached, but suggestively avoided, in a genus of 

 capitellid sea-worms {Clitojiiastus). The whole organism is 



'11 



(I 



A figure of cell division suggesting the internal disruptions and re- 

 arrangements of the nucleus {a) and protoplasm. — From Rauber. 



not sacrificed, but only an abdominal portion of the body. 

 This is in fact one of the keynotes to reproductive differentia- 

 tion, — the sacrifice is lessened, and the fatality thus warded off. 

 But again, we find in some threadworms or nematodes {e.g.^ 

 Ascaris dadyluris) that the young live at the expense of the 

 mother, until she is reduced to a mere husk. In fresh-water 

 Polyzoa, Kraepclin notes that the ciliated embryo leaves the 



