24 



CHLOROPHYCEAE 



have been recorded for Chlamydomonas eiigametos. The zygote on. 

 germination frequently gives rise to four swarmers, and it is 

 probable that meiosis occurs during this segmentation, the normal 

 vegetative cells thus being haploid. In C. pertusa and C. hotryoides, 

 however, the zygote may remain motile for as long as lo days, and 

 hence it may be considered that these two species exhibit a definite 

 alternation of generations. In C. variabilis the persistent quadri- 

 flagellate zygote has for long been known as Carteria ovata (cf. also 

 p. 297), but it has now been shown that the latter is the diploid 

 generation of the Chlamydomonas. 



The genus is widespread, the various species occurring prin- 

 cipally in small bodies of water or on the soil. 



Chlamydomonadaceae : Goniiim {gonium, angle). Fig. 15. 



The colony in the different species is composed of four, eight or 

 sixteen cells all lying in one plane and forming a flat quadrangular 

 plate, but it has been suggested that the four- and eight-celled 



Fig. 15. Gonium pectorale. A-D, stages in the formation of a coenobium. 

 E, colony ( x 520). F, zygote. G, H, stages in germination of zygote. J, four- 

 celled colony. (A-D, after Fritsch; E, after Smith; G-J, after Kniep.) 



