notorious, is none the less manifest. For instance, 

 such fixed forms as many sponges, as the coral, 

 anemone, coralline, comb-jellyfish, oyster barnacle, 

 and sea-squirt have contained in each individual 

 the mechanism producing the spermatozoa and the 

 mechanism producing the eggs. Among vertebrate 

 animals hermaphroditism is rare; but it is known 

 that the human embryo passes through a herma- 

 phroditic condition. However, except in the case 

 of some degenerate forms, parasitic worms, for ex- 

 ample, sexual maturity of both organs in the same 

 individual is not commonly coincident, and cross- 

 fertilization is the usual method by which the 

 species is perpetuated. Then, again, there are some 

 species of flatworms which in early life are males 

 only, but later they lose their masculine characters 

 and become true females. And what is even more 

 strange, still other species appear never to have 

 had the functions of sex; in order to reproduce, 

 they resort to dividing into pieces, each piece grow- 

 ing into a perfect adult. Obviously, this peculiar 

 instance is not a primitive condition; it seems that 

 somehow, in the long struggle for sexual differ- 

 entiation, they lost their functions as well as the 

 fight. 



[180] 



