40 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



SUB-FAMILY I. VOLVOCEJE. 



Motile ccenobia; cells varying in number from 4 to 20,000, 

 globose or ovoiclal, with a distinct but thin cell wall ; cilia two ; 

 chloroplast one of very variable form, usually including a single 

 pvrenoid. Cells usually imbedded in a common mucilaginous 

 investment ; more rarely united by protoplasmic processes. 

 All the cells may be capable of reproducing the plant, or there 

 may be a differentiation into vegetative and reproductive cells. 

 Vegetative reproduction by division of some or all of the cells 

 to form daughter-ccenobia. Isogamous or heterogamous sexual 

 reproduction. 



Key to Genera. 



1. Colonies spherical or circular 2 



Colonies flat, cells 4-16, angles rounded, in a color- 

 less sheath Gonium 



2. No gelatinous covering, cells many, in a hollow globe 



Volvox* 

 No gelatinous covering, cells 16, arranged in four 



rows Spondylomorum* 



With a gelatinous covering 3 



3. Colony ovate or spherical 4 



Colony of eight cells, in an equatorial zone in a 



spherical or ellipsoidal investment Stephanospharra 



4. Cells 16-32, globose, not crowded, but scattered at 



regular intervals on a colorless sphere Eudorina* 



Cells 8, 16, 32, or 64, globose, crowded, often angular 

 from pressure Pandorina* 



Description of Genera. 

 Gonium Muller (inclus. Tetragonium West). Four to 

 sixteen cells so placed in a flat stratum as to form a quadrangle 

 with rounded angles. A colorless tegument covers all. Cells 

 globular except when angular from pressure. The cilia all 

 arise from one surface of the colony. When old, the cells 

 become granular and are connected by produced angles. Re- 

 production by repeated division of the cytoplasm into zoogo- 

 nidia. Multiplication by daughter-ccenobia formed in each cell 

 of the mother-ccenobium. 



