CONJUGATION IN CHLAMYDOMONAS 189 



jugation two gametes swim towards each other 

 (Fig. 21, a), their front ends come into contact, and 

 their bodies gradually fuse completely (Fig. 21, b, 

 Fig. 22, a, b), cytoplasm with cytoplasm, and nucleus 

 with nucleus. When the gametes have cell walls the 

 protoplasmic bodies slip out of them, leaving the 



FIG. 22. Conjugation of Carteria muttifilis, a species with four flagella 

 closely allied to Chlamydomonas : a, beginning of fusion ; b, 

 advanced stage ; c, zygote with eight flagella ; d, zygote with 

 thick wall after loss of flagella. (After Dill.) 



empty shells behind (Fig. 21, c). The single cell formed 

 by the union of the two gametes (Fig. 21, d) is called 

 the zygote (cf. Mucor, p. 162 ; Pythium, p. 175). In some 

 cases the zygote continues to swim for a time with 

 its four flagella, two derived from each gamete 

 (Fig. 22, c this is drawn from a form in which the 



