

Figure 273. — Photomicrograph of a cross section of a ripe spermary of C virginica. Bouin, hematoxylin-eosin. 



the foUicles and of a number of cells at diflferent 

 stages of the development nearer to the walls. 

 The eggs are attached to the walls of the follicles 

 by elongated peduncles, giving them a pear-shaped 

 appearance. At the height of sexual develop- 

 ment the layer of undilTerentiated germinal 

 epithelium is reduced to a very narrow band of 

 small cells hardly visible at low magnification 

 (fig. 272). The connective tissue between the 

 folhcles also very nearly disappears. 



The arrangement of cells in a ripe spermary (fig. 

 273) is similar to that in the ovary. Fully formed 

 spermatozoa are massed together inside the 

 follicle with their tails inward. They become 

 separated as the sperm moves through tlie genital 

 canals, which are frequently distended by the 

 accumulation of spermatozoa ready to be ejected. 

 In 0. edulis and 0. lurida the sperm in the lumen 

 of a follicle form distinct balls which retain their 



shape until they are discharged by the oyster. 

 A number of sex cells remain in the follicles at the 

 completion of spawning. Consequently, at the 

 end of the reproductive season the gonads contain 

 mature ova and sperm as well as undifferentiated 

 cells; many of them are pycnotic and detached 

 from the germinal lining of the wall. Phago- 

 cytosis becomes pronounced as large numbers of 

 leucocytes invade the follicles to digest and 

 cytolize the remaining sex cells (fig. 274). The 

 connective tissue between the follicles becomes 

 disorganized. After the reabsorption of the gonad 

 is completed only a narrow band of germinal epi- 

 thelium remains in a few follicles and the entire 

 layer has shrunk to such a thin band that it is 

 not visible to the naked eye. The oyster is now 

 at an indifferent stage. Its sex can be recognized 

 in some individuals in which young ovocytes or 

 spermatocytes are present, but in many others 



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FISH AND WILDLIFE SERVICE 



