12 THE OYSTER AND THE OYSTER INDUSTRY. 



of the right side of the or^an would present practically the same 

 appearance, there being a similar system of ducts o}>ening on that 

 side beneath the muscle. Through these two openings the genital 

 products are discharged into the water at spawning time. 



LIFE HISTORY. 

 TIK ^F SPA WANING. 



The oyster may spawn when the water reaches a temperature of 

 68° F., but spawning proceeds at normal speed only when the water 

 is 70° or above. For this reason the spawning period varies in 

 different regions, depending on the temperature of the water, which 

 is regulated by the depth of the water and the general meteorological 

 conditions. Shallow bodies of water, even though in more northern 

 latitudes, often become warm as early or earlier than deeper waters 

 farther south. In the north, where the season is shorter, the spawn- 

 ing period is relatively short, often lasting only two or three weeks, 

 while in the south oysters may be found in a spawning condition 

 from early spring until fall. 



In Long Island Sound, the bulk of the oysters spawn about the 

 last of July; in Great South Bay, spawning occurs from about 

 June 5 until after the Fourth of July. In New Jersev waters spawn- 

 ing begins about June 1. SpawT:iing extends in Chesapeake Bay 

 from May until September. On the Gulf coast, spawning begins in 

 March and spa\oiing oysters may be found as late as November. 



REPRODUCTION. 



In spite of the fact that the sex of the oyster can not be distinguished 

 by the external appearance of the shell, of the body, or of the repro- 

 ductive organs, the sexes are separate. Some oysters are male, the 

 reproductive organs developing spermatozoa or milt; other oysters 

 are female and produce ova or eggs. While it has at times been 

 stated that the sex might change from year to year, an oyster being 

 perhaps male one year and female the next, or the reverse, there is 

 no evidence on which to base this belief, except some inconclusive 

 researches made nearly 50 years ago and not borne out by sub- 

 sequent investigations. It can be almost conclusively stated that 

 the sex of the eastern oyster is permanent and does not change 

 during the life of the individual. 



The sexes can be distinguished only by an examination of the 

 products discharged by the reproductive organs. The spermatozoa 

 and eggs are so extremely small that a lens must be employed to 

 distinguish one from the other. The eggs (PI. Ill, fig. 2) vary from 

 roughly pear-shaped to oval or nearly spherical and measure about 

 ■g^ of an inch in diameter. It is estimated that a female oyster will 

 produce over 16,000,000 eggs. The male genital products, or sperma- 

 tozoa, are many times smaller than the eggs. Each spermatozoon 

 (PL III, fig. 1) is made up of a head about io^^oQ - ot an inch in 

 diameter, pointed at one end and flattened at the other. To this 

 flat base is attached a very slender threadlike tail about 20 times 

 the length of the head. This tail lashes about and moves the 

 spermatozoon around in the water after it has been discharged by 

 the male oyster. 



