178 ON ZOOLOGICAL SYSTEMS, AND THE 



(ostrea and mytilus), both which contain species that produce pearls, and 

 mother-of-pearl; though the real pearl-muscle is amya or gaper, found 

 chiefly on the coasts of Malabar and Ceylon, where the principal pearl- 

 fisheries are established. The species of oyster that produces small pearls 

 is sometimes traced on our own shores, and is said to have been at one time 

 frequent in the river Conway, in Wales. Most of the oysters cast their 

 spawn towards the close of the spring, or in the beginning of the summer, as 

 the month of May. This spawn is by the fishermen called SPAT, and in size 

 and figure each resembles the drop of a candle. As soon as cast or thrown 

 off, these embryon disks adhere to stones, old oyster-shells, pieces of Wood, 

 or whatever other substance comes in their way; a calcareous secretion 

 issues from the surface of their bodies, and in the course of twenty-four 

 hours begins to be converted into a shelly substance. It is two or three 

 years, however, before they acquire their full size. 



The scallops, which are a tribe belonging to the oyster kind, are capable 

 of leaping out of the water at pleasure, to the distance of half a yard: when 

 elevated they open their shells, and eject the water within them, and then 

 falling back- into the water close them with a loud snap. 



Among the more elegant of this division is the nacre, pinna, or sea-pen, so 

 called from its form ; the animal of which (a limax or slug) secretes, as we 

 have already observed, a large quantity of fine strong silky hair, or beard, 

 which by the Italians is woven into a kind of silky plait. And among the 

 most extraordinary is the gigantic chama or clamp-shell, in form resembling 

 the oyster: one species of which we noticed not long since, as found ill the 

 Indian Ocean, of the weight of between five and six hundred pounds ; the fish 

 or inhabitant large enough to furnish a hundred and twenty men with a full 

 meal, and strong enough to lop off a man's hand, and cut asunder the cable 

 of a large ship. 



Of the MULTIVALVED TESTACEOUS WORMS, or those containing more than two 

 shells, there are but three known species, the chiton, the lepas or acorn-shell, 

 and the phloas, or, as it is often improperly called, pholas, so denominated 

 from its secreting a phosphorescent liquor of great brilliancy, which illumi- 

 nates whatever it touches or happens to fall upon, and to which Linnaeus 

 chiefly ascribed the luminous appearance which the sea often assumes at a 

 distance : a subject, however, which we shall have occasion to examine 

 hereafter. 



The FOURTH CRDER of the Linuaean class of WORMS is called ZOOPHYTES, or 

 PLANT-ANIMALS, so denominated from their efflorescing like plants. Most of 

 them are of a soft texture, as the hydra or polype, so well known from its 

 being capable of existing when turned inside out, and of reproducing any part 

 of its tentacles or body when destroyed by accident. Some are corky or 

 leathery, as different species of the alcyonium ; some bibulous, as the spongia 

 or sponge, which is now decidedly ascertained to be an animal substance ; 

 and some calcareous, as the numerous families of coral, which, under the 

 form of tubular, starry, or stony stems, are denominated tubipores, madre- 

 pores, and isises. 



The FIFTH or INFUSORY ORDER OF WORMS, comprehends those minute and 

 simple animalcules which are seldom capable of being traced, except by a 

 microscope ; and, for the most part, reside in putrid infusions of vegetables, 

 or in stagnant waters filled wuh vegetable matter. Of these, the smallest 

 known species is denominated monas. To a glass of the highest magnifying 

 power it appears nothing more than a minute simple point or speck of jelly, 

 obviously, however, evincing motion, but often from its delicacy seeming to 

 blend itself with the water in which it swims. 



Such is a bird's eye view of the Linnrean class of worms, and its 'five orders 

 of intestinal, molluscous, testaceous, zoophytic, and infusory animals. 



The INSECTS form the NEXT CLASS in an ascending scale; classically cha- 

 racterized as small animals, breathing through lateral spiracles, armed on 

 all sides with a bony skin, or covered with hair; furnished with numerous 

 feet and moveable antennae or horns, which project from the body, and are 



