EUPHYCOPHYTA 



21 



reticulata), some have one (C. stellata), or two (C. de baryana), or 

 several (C. gigantea). The chloroplast may be reticulate (C. reticu- 

 lata), or axile and stellate (C. eradians), or it may be situated later- 

 ally (C. parietaria). It has been said that under cultural conditions 

 many of the characteristic features can be modified, and that there- 

 fore some of the species are not strictly species but are simply 

 phases in the life cycles of other' species. 



Fig. 2 Chlamydomonas. A, B, vegetative individuals of two parents. 

 Azj Bz, zygotes of parents. A x B, fusion between gametes of A and 

 B. ABz, zygote of hybrid. Fi, four hybrid individuals obtained from 

 germination of one heterozygote. C, Chlorogonium ooganum, 

 female showing formation of ovum. D, Chlorogonium ooganum, 

 male showing formation of antherozoids. E-G, stages in fusion of C 

 media ( x 400). H, vegetative division in C. angulosa. I, zygote of 

 C coccifera. J, conjugation in C. longistigma ( x 400). K, fusion of 

 naked gametes of C. pisiformis ( x 400). L-N, stages in fusion of 

 gametes of C. braunii. O, fusion of gametes in C. coccifera. P, C. 

 hrauniiy palmelloid stage. (A-D, after Fritsch; E-K, after Scott; 



L-Pj after Oltmanns.) 



The motile cells are spherical, eUipsoid, or pyriform in shape 

 with a thin wall which occasionally possesses an outer mucilage 

 layer. The two flagella are situated anteriorly and either project 

 through one aperture in the wall or else through two separate canals, 

 but in either case at the point of origin of the flagella there are 

 two basal granules or blepharoplasts (see p. 18). Each cell typically 

 possesses two contractile vacuoles which have an excretory func- 

 tion. 



