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GERMINAL ORGANIZATION INDUCTION PHENOMENA 



bc 



bc 



C i* # 



Fig. 6. Electron mic ruscopic pictures ( x 5830J ui' ihe cortex of frog oocytes, (a) at the ap- 

 pearance of the first yolk platelets (y) : the cortex contains the layer of cortical granules (c), 

 the basal cortical cytoplasm (be) and the zone of microvilli (v) which correspond to the 

 zona striata and have protruded gradually; protoplasmic follicular cells (i) extend toward 

 the microvillous layer. 1, lipochondria, m, mitochondria; (b) similar region at a later 

 stage: the cortical granules have enlarged, the basal cortical cytoplasm is now folded into 

 alternating ridges and valleys, and the microvilli extend from the peaks of the ridges. Note 

 also that the follicular processes (f) traverse the space between oocyte and inner follicle 



cells (i). Courtesy of Kemp, 1956. 



oyster, the stalk of the pear-shaped oocyte is indicative of the former implantation 

 on the gonadic epithelium. Moreover, this region remains free of yolk and forms 

 an antipolar plasm filled with ribosenucleic acid (or RNA) ; no chorion deposit 

 appeared there, so the membrane preserves a definite landmark (Fig. 2) of the 

 antipole (Pasteels and Mulnard, 1957). In non-tubular ovaries, such a relation 



