in zoology, see Ostrea.

The oyster affords the curious in microscopic observations a very pleasing entertainment. In the clear liquor many little round living animalcules have been found, whose bodies being conjoined, form spherical figures, with tails not changing their place otherwise than by sinking to the bottom, as being heavier than the fluid; these have been seen frequently separating, and then coming together again. In other oysters, animalcules of the same kind were found, not conjoined, but swimming by one another, whence they seemed in a more perfect state, and were judged by Mr Lieuwenhoek to be the animalcules in the roe or semen of the oyster.

A female oyster being opened, incredible multitudes of small embryo oysters were seen, covered with little shells, perfectly transparent, and swimming along slowly in the liquor; and in another female, the young ones were found of a browner colour, and without any appearance of life or motion.

Monsieur Joblot also kept the water running from oysters three days, and it appeared full of young oysters swimming about nimbly in it; these increased in size daily; but a mixture of wine, or the vapour of vinegar, killed them.

In the month of August oysters are supposed to breed, because young ones are then found in them. Mr Lieuwenhoek, on the 4th of August, opened an oyster, and took out of it a prodigious number of minute oysters, all alive, and swimming nimbly about in the liquor, by means of certain exceeding small organs, extending a little way beyond their shells; and these he calls their beards. In these little oysters, he could discover the joinings of the shells; and perceived that there were some dead ones, with their shells gaping. These, tho' so extremely minute, are seen to be as like the large oysters in form as one egg is to another.

As to the size of them, he computes, that 120 of them in a row would extend an inch; and consequently, that a globular body, whose diameter is an inch, would, if they were also round, be equal to 1,728,000 of them. He reckons 3000 or 4000 are in one oyster, and found many of the embryo oysters among the bairds; some fastened thereto by slender filaments, and others lying loose; he likewise found animalcules in the liquor 500 times less than the embryo oysters.

It is not very uncommon to see on oyster-shells, when in a dark place, a shining matter or bluish light, like a flame of brimstone, which sticks to the fingers when touched, and continues shining and giving light for a considerable time, though without any sensible heat. This shining matter being examined with a microscope, was found to consist of three sorts of animalcules; the first whitish, and having 24 or 25 legs on a side, forked, a black speck on one part of the head, the back like an eel with the skin stripped off. The second sort, red, resembling the common glow-worm, with folds on its back, but legs like the former; a nose like a dog's, and one eye in the head. The third sort, speckled, with a head like a foal, with many tufts of whitish hairs on the sides of it. Some much larger and greyish might be seen, having great heads, two horns like a snail's, and six or eight whitish feet; but these did not seem to shine.