190 GERM-CELL CYCLE IN ANIMALS 



All the species of METAZOA may be separated into 

 two groups. The individuals in one group of species 



FIG. 56. Diagram of the reproductive organs of the earthworm, dorsal 

 view. A, B t C, seminal vesicles ; N, nerve-cord ; 0, ovary ; OD, ovi- 

 duct ; R, egg sac ; S, spermatheca ; SF, seminal funnel ; T, testes ; 

 VD, vas deferens. (From Marshall and Hurst.) 



possess only one sort of reproductive organs (male or 

 female) and produce only one sort of germ cells (eggs 

 or spermatozoa) ; these species are said to be dioa- 



