PROTOZOA 



27 



(Fig. 25) form merogametes of two sizes and are definitely ani- 

 sogamous. Volvox (Fig. 46) and related forms have an anisogamy 

 in which the female gamete is a hologamete (oogamy). A similar 



Fig. 25. Anisogamous syngamy of Chlamydomonas . a-h, C. media, after 

 Klebs. a, Vegetative individual, h, Eight gametes produced inside the cuticle 

 of the parent, c, Single gamete, d, Gamete before syngamy showing 

 protoplasm at one end of the cuticle, e, /, g, Syngamy between two gametes 

 of unequal size : the individuals slip out of the cellulose cell at the time of 

 fusion, the cilia withdraw and there is a complete fusion of the individuals. 

 h, The resultant thick-walled zygote, i, j, k, C. brauni, after Goroschankin : in 

 this species the gametes fuse whilst yet within their cellulose walls and there is 

 marked anisogamy, the small gamete slipping into the cuticle of the larger 

 gamete, j. Shows the nuclei, chloroplasts and pyrenoids of the two gametes 

 still separate, k, Shows the fused nuclei. 



series is shown by the Sporozoa. The syngamy of some species of 

 Monocystis, for instance, is isogamy of merogametes, that of others 

 is anisogamy of merogametes with various degrees of unlikeness 



