GENERATION, SEX AND ONTOGENY 



215 



Fig. 121. — Stentor reproducing hy fission. 

 (After Stein.) 



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



modern })liilosophical biologists. There is a faUacy, liowever, 



in the phrasing, l^ecaiise, 



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, 



Avliich 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 ])art 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 sporulalion, 

 or where the l)ody 

 of one individual 

 subdivides into 

 more than two 

 l)arts (as in binary 

 fission), these parts, 

 each of wliich is 

 usually sul)spherical 

 or ellipsoidal num- 

 bering ]) e r h a [> s 

 many Inuidreds. 

 A condition known as parlhcjwgcncsis is foimd amont^ 



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

 sented by individuals of both sexes, the female can produce 





Fig. 122. — Holophrya nuiUifdiis, an infusorian parasitic 

 on fishes reproducing by sporulalion. 



