PARENTAGE. 47 



as to be optically pure, and has had similar results. So 

 that we may consider the question to be scientifically 

 settled, and that all living beings come from similar 

 parentage, or, as Virchow expresses it, " omnis cellula 

 e cellula" (every cell is from a cell.) 



12. Parentage is of two kinds, sexual and non-sexual. 

 In the first, we sometimes find the sexes distinct, as in 

 the higher animals, and sometimes united in the same 

 Individual, as in the stamens and pistils of most flowers, 

 and as in some animal forms. 



Non-sexual generation is seen mostly in the simpler 

 forms of animal and vegetable life, and as it throws light 

 on many of the phenomena of nature which would other- 

 wise be obscure, we notice this form of reproduction here 

 in a general way, reserving special instances until we 

 treat of the life-history of each class. 



13. In referring to the Vorticella, or bell-shaped ani- 

 malcule, in our first chapter, mention was made of its in- 

 crease by self-division. The mass of bioplasm of which 

 it is composed separates into two masses, which become 

 separate individuals. This mode of increase is called 

 Fission, and is quite common among the minuter forms 

 of life. In Sarcina ventriculi, a sort of vegetable para- 

 site, the division is into fours, or four times four. 



14. A variety of fission, called Gemmation, or Bud- 

 ding, is often met with. A portion projects from the 

 mass, and separates to begin an individual existence. 

 Thus in the fresh-water polyp, or Hydra, a bud gives 

 rise to an organism like the parent, which becomes de- 

 tached and independent. Sometimes the product of 

 buds remains attached, as in plants, and in the Foram- 



