348 



SENESCENCE AND REJUVENESCENCE 



195 



FIGS. 192-195. The differentiation of parthenogenic and zygogenic eggs: Fig. 

 192, ovarian tubule of Sida (daphnid crustacean), showing primitive germ cells, pc, 

 and groups, g g, of eggs, o, and nurse cells; Fig. 193, part of a tubule containing a 

 zygogenic egg, o; Fig. 194, ovarian tubule of M ' elanoxanthum (plant louse), showing 

 nutritive gland, o gl, parthenogenic egg, o, and embryo, em; Fig. 195, ovarian tubule 

 of M elanoxanthum, showing nutritive gland, o gl, and zygogenic egg, o. Figs. 192, 193, 

 from Weismann, '77; Figs. 194, 195, from Tannreuther, '07. 



