The Oysters 



five-hundredth of an inch in diameter, with tufts of cilia in bands 

 around it. The whirhng milhons of young "fry" give the water 

 a cloudy appearance, and the oyster-grower is nervous with 

 apprehension. The important thing is the settling of these 

 free youngsters. It occurs after a day or two. If the weather is 

 warm, the surface of the water smooth, and the bottom strewn 

 with shells, a good "set" may be expected. But a cold spell kills 

 millions, and a boisterous sea drifts millions out into deep water. 

 The "spat" once settled is fixed for life. It may survive or 

 perish, but it is utterly passive. Glued to its support, the oyster 

 assumes its characteristic form, though scarcely larger than a 

 pin head. 



The growth of a shell demands a constant supply of lime in 

 solution. The disintegrating of dead shells furnishes this lime 

 food in abundance. As if by instinct the spat chooses for its 

 resting place a rough, limy surface. Old beds furnish plenty of 

 shells. Living and dead oyster shells are coated with spat each 

 season. 



Besides the lime so essential for shell formation, an oyster's 

 food consists of animal and plant organisms of minute size that 

 breed in flocculent mud. The young larvae of crabs and sponges, 

 and mollusks, including oyster spawn and fry, are added to infu- 

 sorians and diatoms. Clouds of these microscopic forms rise in 

 the water to settle again as daylight fades. Coming and going 

 they pay toll to the oysters. 



Roughly speaking, each year of an oyster's life adds an inch 

 to the length of its shell. June spat is as big as a finger-nail in 

 the late autumn. The shell lengthens for about ten years. After 

 that it grows in thickness. The full development of the repro- 

 ductive powers is reached at four years, though spawning begins 

 much earlier. The average oyster's natural life is about ten years. 

 In easy circumstances undisturbed oysters have acquired size 

 and thickness that warrant the estimate of an extreme age limit 

 of fifty years. Layers of the shell indicate different periods of 

 growth, but these do not tally with years. Growth is generally 

 confined to the summer months. Winter is spent in comparative 

 hibernation. Summer may be divided into periods of quiescence 

 and growth, registered by several thin layers of shell. The rate 

 depends upon the length of the growing season and the abundance 

 of the required food elements. 



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