SPECIALIZATION AND ORGANIZATION. 7 



together in roving colonies. Some of these were 

 dominated by a gregarious instinct only, and have 

 clung tenaciously to self-freedom, refusing to make any 

 sacrifice of personal independence for the sake of a 

 physiological union. A few such aggregates, whose 

 freedom has been the forfeit of all advancement, still 

 survive, as exemplified in some members of the Volvox 

 family. In Gonium, for example, the colony consists 

 of a few (4-16) flagellate cells, adhering together in 

 plate-like form, each self-moving, self-feeding, and self- 

 propagating. 



Among these colonial aggregates, there were some, 

 however, which found out how to take one or two simple 

 steps in labor partnership, and thus advanced to a rudi- 

 mentary kind of composite individuality. An interesting 

 example is seen in the famous Volvox of Leeuwenhoek, 

 in which the evolutionists of last century found a con- 

 firmation of their idea, that the germs of plants and ani- 

 mals are preformations in miniature, incased one within 

 the other. The division of labor is here of such an 

 elementary order, that, as BiitschU has suggested, we 

 may look upon a Volvox colony as a near ally of those 

 simple forms from which all the higher plants as well 

 as the Metazoa arose. 



The Volvox colonies, composed of numerous individ- 

 uals, often more than a thousand, are attached to the 

 inner surface of a colonial envelope, at equal distances. 

 In each colony we find two kinds of cells ; one with 

 two fiagella for locomotion, the other without such 

 appendages, fulfilling the work of reproduction. This 

 sinsfle division of labor makes one class of individuals 

 the propagators of the species, the other the preservers 



