MATERIALIST MONISM 



of unicellular organisms into little cell-clusters, 

 and the division of labor arising under the new 

 environment produces the first multicellular ani- 

 mals, the gastraeades. These repeat on a higher 

 plane the primitive division of labor of the pro- 

 tozoa, producing the skin-and-stomach type of 

 the gastrula, which represents the first rudi- 

 mentary plan of connective tissue and internal 

 organs. The unicellular plants have in the 

 meantime accomplished similar results. 



No sooner has this stage become fairly estab- 

 lished, than a new division of labor is inaugu- 

 rated. So long as the cell lives independently, 

 it propagates by fission or gemmation. But in 

 the multicellular community, fission is a nuisance. 

 Gemmation permits of modifications which do 

 not disturb the communal life. So each cell in 

 the community transmits its share of sexual life 

 to special sex-cells, and in the further selection 

 of these the male and female organs arise, lead- 

 ing to the climax of separation of sexes in in- 

 dividuals. Some still retain the old form of 

 common sexuality, but the new mode of propa- 

 gation proves superior in spite of its apparent 

 slowness and complexity, because it furnishes a 

 greater variety of new material for natural selec- 

 tion. 



179 



