32 



THE INVERTEBRATA 



parents, sex may be said to exist among protozoa, but it is rarely that 

 (as in the sporozoon Cyclospora, etc.) the sexes may be distinguished 



Fig. 25. Anisogamous syngamy of Chla?nydomonos. a-h, C. media, after 

 Klebs. a, Vegetative individual. 6, Eight gametes produced inside the cuticle 

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

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

 unequal size : the individuals slip out of the cellulose wall at the time of fusion, 

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

 resultant thick-walled zygote, z, j, k, C. braiini, 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. 



by other features. In many of the Telosporidia (e.g. Monocysfis, 

 Fig. 78) sexual congress may be held to occur, in that individuals, 

 male and female in cases of anisogamy, apply themselves together at 



