THE OYSTER. 51 



one time in a small tumbler of water a number of 

 active and healthy oysters, greater, many times, than 

 the whole human population of Maryland. 



If several oysters are opened during the breeding 

 season, which varies according to locality and climate, 

 as will hereafter be shown, a few will be found with 

 the reproductive organ greatly distended and of a 

 uniform opaque-white color. These are oysters which 

 are spawning or ready to spawn, that is, to discharge 

 their eggs. Sometimes the ovaries are so gorged 

 that the ripe eggs ooze from the openings of the 

 oviducts before the mass is quite at the point of 

 being discharged. If the point of a knife be pushed 

 into the swollen ovary, a milk white fluid will flow 

 out of the cut. Mixing a little of this with sea water, 

 and placing it on a slide underneath a cover, a lens of 

 loo diameters will show, if the specimen is a female, 

 that the white fluid is almost entirely made up of 

 irregularly, pear-shaped, ovarian eggs, each of which 

 contains a large, circular, transparent, germinative 

 vesicle, surrounded by a layer of a granular, slightly 

 opaque yolk. Perfectly ripe eggs will be seen to be 

 clean, sharply defined, and separate from each other. 

 If the specimen be male, a glance through the micro- 

 scope shows something quite different from the fluid 

 of a female. There are no large bodies like the eggs, 

 but the fluid is filled with innumerable numbers of 

 minute granules, which are so small that they are 

 barely visible when magnified 100 diameters. They 

 are not uniformly distributed, but are much more 



