PH YTOMONADIDA 



113 



Genus Volvox Linne. Often large spherical or subspherical 

 colonies, consisting of a large number of cells which are dif- 

 ferentiated into somatic and reproductive cells. The former are 

 numerous and embedded in the gelatinous matrix of colony. 

 The somatic cell contains a chromatophore, one or more pyre- 

 noids, a stigma and several contractile vacuoles. In some there 



I V V ,v „ . 



Fig. 39 a. Eudorina elegans. X235 (After Goebel). 



b. Pleodoritia illinoisensis. X150 (After Kofoid). 



c. Volvox globator. X about 150 (After Janet). 



d. V. aureus. X80 (After Klein). 



e. Polytoma uvella X250 (After France). 



f. Parapolytoma satura X600 (After Jameson), 

 g, h. Phacotus lenticularis. X325 (After Stein). 



i. Pteromonas angidosa. X500 (After West). 



are protoplasmic connections between two neighboring somatic 

 cells, in others such connections apparently do not exist. The 

 generative cells are few and large. Both mono- and bi-sexual 

 reproductions occur. The monosexual gametes are usually 

 fewer and larger in size than the bisexual gametes, and each 

 produces a young colony by repeated division. Bisexual 



