12 HEREDITY AND SELECTION IN SOCIOLOGY 



entiated. Thus Pandorina is composed of sixteen cells, joined 

 together by a gelatinous substance. Eacb of these sixteen cells 

 possesses a nucleus, a contractile vacuole, and a flagellum or 

 lash, which serves as the organ of locomotion. Each cell pos- 

 sesses the faculty of reproducing the entire cell colony ; thus 

 each cell is capable not only of maintaining individual life, but 

 of securing the persistence of the species. Each of the com- 

 ponent cells of Pandorina, after a certain period of growth, goes 

 through a process of divisions into two, four, and finally sixteen 

 daughter cells of identical composition, so that instead of the 

 sixteen original cells there are now 16 x 16 daughter cells = 256. 

 These, united in sixteens, as in the original colony, form sixteen 

 distinct colonies. 



Thus we have in Pandorina an elementary form of multi- 

 cellular organism, almost undifferentiated, and forming an 

 intermediate type between the Protozoa and the higher organisms. 

 Another genus of the same family — Volvox — shows us distinctly 

 the beginnings of differentiation. Here the colony is composed 

 of two kinds of cells, the one kind being diminutive and 

 numerous, the other kind less numerous and of larger dimensions. 

 The former are the somatic cells, adapted to the maintenance 

 and repair of the individual life ; the latter are the re'productive 

 cells. There is as yet no differentiation between the various 

 somatic cells ; each appears to fulfil the same series of functions. 

 But there is in Yolvox a differentiation of the reproductive cells 

 into two kinds — male and female. 



In another related form — Eudorina — the component cells are 

 wholly undifferentiated into somatic and reproductive cells. 

 Each cell possesses the faculty of reproduction, and is at the 

 same time adapted to the maintenance of the individual life. 

 When we speak of the " reproductive cells " of this type, we mean, 

 therefore, all its cells indiscriminately. Yet, although the 

 primary distinction between somatic and reproductive cells has 

 not yet been established, the cells have undergone a differentia- 



