THE VOLVOCIN^: 209 



Pandorina. Its colonies, measuring from *i to "15 mm. in 

 diameter, are spherical or oval, composed of thirty-two, rarely 

 of sixteen cells, which differ from those of Pandorina in being 

 rounded, embedded at some distance from one another at 

 regular intervals in the colonial envelope, and in the fact that 

 their inner ends do not reach to the centre of the colony 

 (fig. 45). The colonies multiply by repeated division of their 



Fig. 45- 



Eudorina. elegans. The colony consists of thirty-two 

 flagellate cells, situated at some distance from one 

 another, and enclosed in a common colonial envelope. 

 cv, contractile vacuoles ; , nucleus ; am, amylum, 

 bodies ; en, colonial envelope. (After Stein.) 



component individual cells, so that daughter colonies are 

 formed much in the same way as in Pandorina. The process 

 of cell-division is somewhat different, but the details need not 

 be considered here. During the formation of the daughter 

 colonies the envelope of the mother colony becomes very thin, 

 and eventually it bursts and liberates the daughter colonies 

 already provided with their flagella and colonial envelopes. 

 After multiplying for several generations in this manner a 

 generation of Eudorina colonies appears, the members of which 

 do not differ in structure from ordinary colonies, but show a 



