348 



SENESCENCE AND REJUVENESCENCE 



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194 



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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 Melanoxanthum (plant louse), showing 

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

 of Melanoxanthum, showing nutritive gland, o g!, and zygogenic egg, o. Figs. 192, 193, 

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



