COLONIES (EUDORINA, VOLVOX) 



189 



ment, and often being easily recognisable where they traverse the 

 latter (Fig. 99, A). By the united action of the cilia of all 

 the individuals, the whole colony moves rapidly through 

 the water, exhibiting a simultaneous rotation upon its axis. 

 Reproduction is usually effected by the subdivision of each 

 of the constituent cells to form as many small daughter-colonies 

 (Fig. 99, B), which are subsequently liberated by the breaking 

 down of the mucilage-investment of the parent. Occasional 



FIG. 100. Volvox. A, Colony of V. aureus (after Klein) enclosing 

 five daughter-colonies, the latter already exhibiting the large cells 

 (d.) from which another generation will be developed. B, Section, and 

 C, surface view of single cells of V. globator (after Meyer) . g., mucilage- 

 layer of cell-wall. 



specimens of Gonium (Fig. 101, E), in which 16 Chlamydomonas- 

 like cells are combined to form a flat plate, are not uncommonly 

 associated with Eudorina. 



The spherical colonies of Volvox (the globe animalcule), 

 sometimes found in large quantities in fresh-water, are far more 

 elaborate. Since they are composed of several thousand cells, 

 they are of quite appreciable dimensions (usually about the size 

 of a pin's head) and readily visible to the naked eye (Fig. loo, A). 

 The constituent cells (Fig. 100, B, C) show more resemblance to 



