GENERATION, SEX AND ONTOGENY 



215 



FIG. 121.- 



-Stentor reproducing by fission. 

 (After Stein.) 



often be met with in the writings of Weismann and certain other 



modern philosophical biologists. There is a fallacy, however, 



in the phrasing, because, 



as a matter of fact, the 



protoplasm of a given 



protozoon gradually loses 



its vitality with con- 

 tinued division until it 



ultimately is unable to 



divide further or indeed 



to perform the other life 



functions: it dies of old 



age. 



Hardly less simple is 



generation by budding, 



which in its simplest 



character is the breaking 



off from one individual 



of a part smaller than a 



half, often, indeed, only 



a very small fractional part, which budded off part has the 



capacity of growing and developing into a new individual like 



its parent. 



A still other 

 mode of generation 

 of simple type is 

 that of sporulation, 

 or where the body 

 of one individual 

 subdivides into 

 more than two 

 parts (as in binary 

 fission) , these parts, 

 each of which is 

 usually subspherical 



FKJ. 122,Holophrya imiltifiliis, an infusorian parasitic Or ellipsoidal, milli- 

 on fishes reproducing by sporulation. beHng perhaps 



many hundreds. 



\j 



A condition known as parthenogenesis is found among 

 certain of the complex animals. Although the species is repre- 

 sented by individuals of both sexes, the female can produce 



