



Centimeters 



Figure 267. — Fully ripe C. virginica. The mantle of the right side was dissected above the epibranchial chamber and 

 pushed to the right to expose the pyloric process. A network of canals leads to the single gonoduct through which 

 the sex cells are discharged. Drawn from life. an. — anus; cl. — cloaca; d.br. — right demibranch; g.o. — genital 

 opening; gon. — gonad; m. — mantle; w.t. — water tubes inside the gills. 



Gonadal layers of about 10 mm. thickness were 

 found in large C. giyas (8 inches in height) from 

 Willapa Bay, Wash. (Galtsoff, 1930a, 1932). 



In all species of Crasf;ostrea the bulk of gonads 

 varies from season to season, reaching its maximum 

 shortly before the onset of spawning. The num- 

 ber of sex cells produced during one reproductive 

 period varies, depending on the conditions of the 

 environment. The greatest gonadal development 

 is more likely to be found in the populations of 

 oysters from the nortliern latitudes north of the 



Chesapeake Bay rather than in the south Atlantic 

 and Gulf waters. This is apparently associated 

 with the fact that the reproductive season in the 

 northern latitudes is of short duration, 4 to 6 weeks, 

 whUe in the warmer waters of the south gonadal 

 formation and spawning, continue, with interrup- 

 tions, for several months. In both groups the 

 annual reproductive capacity (i.e., the number of 

 eggs produced annually) maybe of the same order 

 of magnitude or even greater in the southern 

 oysters because of the longer reproductive period. 



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FISH AND WILDLIFE SERVICE 



