NEMATOIDEA. 645 



appears red from the blood with which the intestine is usually gorged. An analoi>;ous species, found on the Eel, 

 was long mistaken for the young of that animal. 



Ofihio.stomii.-i, have the Ijody formed as in the preceding, but the mouth cleft across^ which gives the appearance 

 of two lips. 0. cy^tidicolOy is found in the air-bladder of some Fishes. 



AscARis (the Ascarides), — 

 Have the body round, and slender toward each extrennty. The mouth is furnished with three fleshy 

 tubercles, among whicli there is a short tube, which the animal can protrude as occasion rei|Lures. 



The species are numerous, and inhabit the intestines of many animals. The females, which are far more 

 numerous than the males, have the intestinal canal straight, and an ovary divided into two branches, which is 

 several times longer than the body, and opens Ijy a single oviduct at about one-fourth of the length from the 

 anterior extremity. The males have also a single vessel, very long, and with the external organ, which is near 

 the tail, sometimes double. Two white filaments, one extending- along the back, and another along the belly, 

 have been considered as nerves ; and two thicker ones, extending along the right and left sides, have been con- 

 sidered as muscles, as a circulating system, and even as a breathing apparatus. Some species, as A. lumbricdides, 

 have the head without lateral membranes. This species is found, without any remarkable difference, in Man, in 

 the Ox, the Hog, and all the varieties of the Horse family ; it has sometimes occurred lifteen inches in length. It 

 is naturally of a white colour; and, from what has been said of its reproductive organs, its power of multiplication 

 is excessive. It occasions disease, and even death, especially in children, or in all cases where it ascends from 

 the intestines into the stomach. A. venniculari.s-, which has a small membrane on each side of the head, is very 

 common in children, and also in adults, when afflicted with certain diseases. It chiefly inhabits the rectum, at 

 the extremity of which it causes intolerable itching. Its length is not more than half an inch, and its body is 

 thickest in the anterior part. It is an exceedingly active little animal, and derives its name from the Greek verb, 

 " to leap, or move.'* 



Strongylus, — 

 Have the body round, and the vent of the male inclosed in a sort of purse variously formed, whicli is 

 regarded as the sheath of the organ of generation, which can be protruded from it. The female is 

 witliout this apparatus, and thus more nearly resembles tlie Ascarides. 



Some species have the mouth ciliated, or toothed, among which is .SI. equinus, which is about two inches long, 

 with a hard spherical head, small soft spines round the mouth, and three lobes in the caudal appendage. It is 

 very common in the intestines of the Horse ; and, so far as is known, in those of all the sohpede family of pa- 

 chydeiinatous animals. Sometimes it makes its way to the arteries, and there occasions aneurisms, and other 

 unpleasant diseases. 



Other species have the mouth with tubercles, or papillre, and among these one of the most remarkable is 

 S. giga.-i, the largest worm which is known to inhabit the intestines of any animal. It grous to the length of two 

 or three feet, and is as thick as the little finger. It is usually found in the kidneys of vailous animals, as the 

 Wolf, the Dog, the Marten, and even Man ; where it is coiled up, and inflates the organ, causing great pain. 

 Sometimes small ones pass off with the urinary discharge. It is not, however, confined to the kidneys, but is 

 met with in other viscera. Its usual colour is a fine red; the mouth has six papilL-e ; the intestine is straight, 

 with cross furrows ; the ovary is simple, and three or four times the length of the body. It is understood to have 

 a posterior opening, and also one near the mouth. M. Otto has considered a slender white thread, which passes 

 along the abdomen, as being the nervous system. 



t^inroptenis, have been separated from the Ascarides. They have the termination of the body spiral, with two 

 wing-like membranes, between which is the reproductive organ. One species is occasionally found in the human 

 bladder, and another in the stomach of the Mole,— to the villous coat of which it attaches itself by a smaU tubercle. 

 Phijsolopiera, has a small bladder between the wing-like membranes. Sclerottoma, has the mouth furnished 

 with six small scaly plates. It is found in the Horse and the Hog. Lior/ii/nc/ius, has the mouth in the form of a 

 small proboscis, with which it penetrates the cavity of the viscera. 



Pt'iitasionia, have the body flattened, and sharp in the sides, and the transverse rug^ crcnulated. The skin is 

 tliin and weak ; the head broad and flat, with the mouth beneath, and a longitudinal slit on each side, from which 

 issue the hooks whereby the animal adheres. Tlie intestine is straight, and the reproductive organs long and 

 tortuous. A white filament surrounding the mouth, and two filaments which proceed from it, appear to be the 

 nervous system. One species, P. tit'/iw'idcs, occurs m the frontal sinuses of the Horse and Dog, and attains a 

 length of about six inches. Prionoderma, resemble the former, only the mouth is terminal, and has two 

 small hooks. 



Cuvier includes the following genera of intestinal worms in this order, but gives it as his opinion that, 

 when they are l)etter known, they will require subdivision as a distinct family. 



Lern.ea, — 

 Have the body resembling the former both in its external and its internal organisation ; hut it is pro- 

 longed into a sort of neck of a horny consistency, at the end of which is the mouth, variously armed 

 with plate-like aiipendagcs. It insinuates the mouth and tliese appendages into the gills of fishes, 



