12 THE OYSTER AND THE OYSTER INDUSTRY. 



of the right side of tlie organ would present practically the same 

 aopearance, 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. ' 



TU^' v>F SPAWNING. 



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 tliis reason the spawning period varies in 

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

 is regidated by the ae[)th of the water and tlie 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 f all- 

 in Long Island Sound, the bulk of the oysters spawn al)Out the 

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

 June 5 untU after tlie Fourth of July. In New Jersev waters spawn- 

 ing begins about June 1. Spawning extends in Chesapeake Bay 

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

 March and spawning 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 i^ermanent 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 

 distin^ish one from the other. The eggs (PI. Ill, fig. 2) vary from 

 rouglily pear-shaj>ed to oval or nearly spherical and measure about 

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

 produce over 1 0,000,000 eggs. The male genital products, or sperma- 

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

 (PL III, fig. 1) is made up of a head about kj.^qoo o* ^^ i"^^ ^P^ 

 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 tlie head. This tail lashes about and moves the 

 sj)ermatozoon around in the water after it has been discharged by 

 the male oyster. 



