BIVALVE MOLLUSC A. 375 



to the mouth and tentacles ; the second, to the respiratory branchiae. 

 With organs of the senses oysters are unprovided. Condemned 

 to a sedentary life, riveted to a rock where they have been rooted, 

 as it were, in their infancy, they neither see nor hear ; touch appears 

 to be their only sense, and that is placed in the labial tentacles of 

 the mouth. 



The mode of reproduction in these creatures is very peculiar. 

 The oyster unites in itself the functions of both sexes. In the same 

 organ are found the eggs — called spat — and the mobile corpuscles 

 intended to fertilise them. 



The eggs are yellowish in colour, and exist in prodigious numbers 

 in each individual. We are assured that an oyster may carry as many 

 as two millions of eggs ! Nature always makes ample provision for 

 the preservation of species ; but in spite of the most ample provision 

 here displayed, man, in his reckless and wasteful gluttony, has all 

 but defeated Nature. A tyro can compute how many individuals a 

 bank of oysters reckoned at 20,000 would produce, at the rale 

 of 2,000,000 — or 800,000, as other authorities assert — from each one 

 annually, and it will amount to an incredible number — in fact, each 

 would multiply itself by millions in three years ; and yet, thanks to 

 our improvident management, oysters get scarcer every year. 



The spawning season is usually from the month of June to the 

 end of September : during this season the oysters deposit their eggs 

 in the folds of their mantle. During the period of incubation the 

 eggs remain surrounded by mucous matter, which is necessary to 

 their development, the whole having the appearance of a thick cream 

 — this milky appearance being due to the accumulated mass of ova 

 surrounded by the mucus : this mass undergoes various changes of 

 colour while losing its fluidity, becoming successively yellowish, 

 gi-eyish, brown, and violet, a condition which indicates the near 

 termination of the embryo state, for the oysters do not, like many other 

 inhabitants of the sea, eject their ova ; they incubate them in the 

 folds of their mantle, and only discharge them when they can live 

 Avithout maternal protection. Nothing is more curious to witness 

 than a bank of oysters at the spawning season. Every adult in- 

 dividual of which it is composed throws out its phalanx of progeny. 

 A living dust is seen to exhale from the oyster bank, troubling the 

 water and giving it a thick cloudy appearance, which disseminates 

 itself litde by little in the liquid, until it dissipates and loses itself far 

 from its focus of production. The spat is soon scattered far and wide 

 by the waves ; and unless the young oyster finds some solid body to 

 which it can attach itself, it falls an inevitable victim to the larger 



