THE EVOLUTION OF MAN 



cluster together and form the first larger clumps 

 of cells. We know many uni-cellular animals 

 that do this to-day. These clusters of to-day are 

 mere aggregations of cells without any attempt 

 at organization, and most likely the primitive 

 uni-cellular clusters were likewise mere group 

 aggregations. But gradually these cell aggrega- 

 tions of primitive times entered into more inti- 

 mate social relations. They developed a certain 

 division of labor. All this came about as a sim- 

 ple consequence of natural conditions. 



All the cells in the cluster wanted to eat, each 

 by itself, so all of them crowded outward when 

 the cluster drifted about in the water. In con- 

 sequence the cluster became a bubble, since all 

 the cells arranged themselves on the surface and 

 left the interior space vacant. This process at 

 this stage is still very well illustrated by the early 

 example of the Magosphaera. Under these con- 

 ditions, the probability was nevertheless that all 

 the rations obtained by the various cells would 

 not be equal. The hollow bubble drifted through 

 the water, or it gradually developed its own mo- 

 tion by the combined efforts of all cells, and thus 

 it rolled against tlie tide. The cells on the up- 

 stream side then obtained most of the food, while 

 the juices of the cells passed through the permea- 



128 



