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BERTRAM G. SMITH 



ery and parallel to the newly-formed zona radiata, but sepa- 

 rated from the latter by a narrow layer of clear cytoplasm (see 

 fig. 22). At this time the ovocyte has a diameter of from 1.5 mm. 

 to 2 mm. The yolk zone is divisible into two layers, an outer 



Fig. 22 Portion of a section through one of the most advanced ovocytes of a 35 

 cm. Cryptobranchvis allcgheniensis, showing structure of the membranes sur- 

 rounding the egg and the distribution of yolk granules. X 340. The strip shown 

 extends about half-way to the germinal vesicle, c, cyst membrane; cy., yolk- 

 free peripheral zone of cytoplasm; ep., inner epithelial membrane of the ovarian 

 wall;/o/., follicular membrane i)ropcr; z. p., zona poUucida; z. r., zona radiata; 

 y. and y' ., layers of fine and coarse j'olk granules respectively. 



layer of fine yolk particles and an inner layer of coarse yolk par- 

 ticles, separated by a narrow region poor in yolk. 



In the largest residual eggs (2 to 3 mm. in diameter) of spent 

 females, the yolk-laden zone has extended inward further than 



