268 REPORT OF COMMISSIONER OF FISH AND FISHERIES, 



streaks if the water be agitated, aud witli no particles distinguishable 

 by the naked eye. 



Another test is to spread out a drop of the genital iiuid, mixed with 

 a drop of water, in a thin film upon a piece of glass, such as a micro- 

 scope slide. If the specimen be a female, an examination with a strong 

 hand lens will reveal many minute pear-shaped or oval bodies or eggs, 

 each with a clear spot, the nucleus or so-called germinal vesicle. If the 

 specimen be a male, the film can not be resolved into distinguishable 

 particles when viewed with the lens, but consists of a milk-white mass, 

 having a quivering appearance owing to the effect of the combined 

 movements of the indistinguishable spermatozoa. 



The histological characters which distinguish the testes and ovary 

 are considered under the head of anatomy. 



According to Professor Schiedt, an hermaphroditic oyster occurs on 

 our northwest coast, the specimens examined coming from the State of 

 Washington, the exact locality not being mentioned. Sexually, there- 

 fore, this species resembles the common oyster of Europe. 



RIPENING OF THE GENERATIVE ORGANS. 



In spring, when the water begins to warm, certain changes begin to 

 manifest themselves in the generative organs, preparatory to the act 

 of spawning. In the female some of the minute eggs in the ovaries 

 increase in size and become loosened in the follicles or little pockets of 

 tissue in which they have undergone their early develo])ment. All of 

 the eggs which are to be discharged in any one year do not ripen at the 

 same time, so that the spawning of each individual extends over a 

 greater or less period. An examination of the ovary at any time will 

 always show great numbers of minute immature eggs, most of these 

 being ova which will i-ipen and be discharged during some subsequent 

 year. Other changes, which it is not necessary to mention here, take 

 place in the eggs and tissues, but the ultimate result is that the ovary 

 becomes enlarged by the growth of the ripening eggs and the latter 

 pass into the oviducts, which stand out as milky-white and much- 

 branched vessels on each side of the body. 



The spermatozoa develop in somewhat the same manner, but the 

 generative cells, instead of developing into eggs, undergo rai)id divi- 

 sion, each into a number of minute active bodies, which pass into the 

 sperm ducts and gorge them with a white fluid, the milt, in general 

 naked-eye appearance closely resembling the ovarian fluid. 



SPAWNING. 



The act of spawning consists m the discharge of the ripe genital 

 products into the surrounding water, where fertilization is left to chance. 



The genital ducts, one on each side, open into the chambers above 

 the gills, and the ova in the one sex and the spermatozoa in the other, 

 gradually oozing out of the openings, are caught up by the currents 

 of water passing through the gill-canals and expelled from the body, 



