THE WONDERS OF LIFE 



have to be hermaphroditic and able to fertilize themselves 

 if the species is to be maintained. On the other hand, 

 many hermaphroditic flowers, although they have both 

 sorts of sex-organs, are incapable of fertilizing them- 

 selves and have to receive this from insect visitors which 

 carry the pollen from one flower to another. 



Individuals of the third order, which we call stocks 

 cormi) in both the plant and animal worlds, also exhibit 

 varying features in the sex-persons which compose them. 

 When male and female diclinic sprouts or persons are 

 found side by side on the same stock, we call this her- 

 maphrodism of the cormi mo;za?aa ("one-housedness "); 

 this is the case with most of the siphonophora and some 

 of the corals. Dicecia (" two-housedness") is less com- 

 mon : in this one stock has only male and the other only 

 female sprouts or persons, as in poplars and osiers, most 

 of the corals, and some of the siphonophora. The phys- 

 iological advantages of crossing — the union of sex-cells 

 of different individuals — favor progressive sex-division 

 in the higher organisms. 



A comparative study of the features of hermaphro- 

 dism and sex-division in the plant and animal worlds 

 teaches us that both forms of sex-activity are often 

 found in closely related organisms of one and the same 

 group, sometimes even in different individuals of the 

 same species. Thus, for instance, the oyster is usually 

 gonochoristic, but sometimes hermaphroditic; and so 

 with many other moUusks, vermalia, and articulata. 

 Hence, the question often raised, which of the two forms 

 of sex-division is original, is hardly susceptible of a 

 general answer, or without relation to the stage of in- 

 dividuality and the place in classification of the group 

 under discussion. It is certain that in many cases her- 

 maphrodism represents the original feature; for instance, 

 in most of the lower plants and many of the stationary 

 animals (sponges, polyps, platodes, tunicates, etc.). 



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