1885.] NEW-YORK MICROSCOPICAL SOCIETY. 65 



In these species, as among the fishes, there is a true spawning of 

 eggs by the female, and a fecundating of them in the water 

 which has been fertilized by the presence of the male. But 

 with O. edulis, and O. plicatula, there is no spawning of eggs at 

 all. The eggs are retained between the lobes of the animal, 

 and there hatched, and when emitted into the water, are already 

 well advanced, each having a pair of perfectly formed shells. 



The English oyster, O. edulis, is capable of producing a mil- 

 lion and a half of spawn in a season. But it is shown to a 

 demonstration that our American bivalve, O. Virginiana, can 

 produce in one season, that is, in the r-Iess months, from twenty, 

 to twenty and a half millions of spawn. But these are simply 

 eggs, and do not get the start of the spawn which is emitted 

 already hatched. However, I do think that there is some 

 relation between our American push, and our physical environ- 

 ment. It is a characteristic of the country. An insect ordina- 

 rily well-behaved on the other side of the ocean, so multiplies, 

 if it but immigrate here, as to become a pest and a defiance. 



How does the oyster make his shell ? At a recent meeting 

 of the American Association for the Advancement of Science, 

 a paper was read asserting that the extreme age of an oyster is 

 twenty years. Now I had previously, in an article in the Popu- 

 lar Science Monthly, demonstrated that an oyster might be in 

 fair edible condition at the age of thirty years. Here are the 

 shells of one of the oysters on the characters of which the state- 

 ment was based. This double shell is thirty years old, and the 

 enclosed mollusk was large, and in fair condition. But of this 

 specimen, more anon. In building its shell the oyster starts with 

 the hinge end, at the spot known to conchologists as the umbo. 

 A small plate, or single scale, now represents each valve, and 

 that is the first season's growth. The next season a new growth, 

 or plate, shoots out from underneath the first one, just as 

 shingles do. The oystermen call these laps, or plates, "shoots," 

 and they claim that the number of shoots indicates the years of 

 the oyster. They certainly do contain a record of the seasons, 

 showing the slow-growing and the fast-growing seasons. But 

 there is often great difficulty in clearly differentiating these 

 shoots. The record is often obliterated in places by the growth 

 of parasites, which build their shells or tubes upon the oyster. 

 I have likened these shoots to shingles. Now, at the gable of a 



