a good résumé of the state of our present knowledge of parasitical and wandering nematodes.

The Sclerostomata are distinguished by their mouth being surrounded by a horny armature The river perch usually gives lodging to a viviparous nematode, the Cucullanus elegans, on the development of which a special work has been published. The young ones are provided with a perforating stylet, and penetrate into the bodies of small aquatic crustaceans, called cyclops. When they have obtained entrance into this living lodging, they bore through the walls of the intestines and shut themselves up in the perigastric cavity. cyclops being pursued by the young perch, are swallowed with their guest, and the latter is set free in the midst of the stomach, where it passes through its sexual evolution.

The

Leuckart saw in his aquarium young Cucullani penetrate into the bodies of the cyclops. These crustaceans are therefore the vehicle of these nematodes. Another nematode worm, the Dochmius trigonocephalus, lives at liberty while young, but seeks for an asylum in the dog in its old age. The Sclerostomum equinum causes aneurisms in the horse, which manifest themselves by colic. A hundred of these worms have been found in the same horse. The Sclerostomum pinguicola is very common in the pig in the United States. This is the Stephanurus dentatus of Diezing, noticed by Natterer in Chinese pigs in Brazil. Cobbold notices the same worm as living in the pig in Australia; they have been also found in Germany.

The Strongyli are round, cylindrical worms, with bodies sometimes entirely red, which inhabit different

organs in mammals and birds. A very remarkable species, the Strongylus gigas (Fig. 66), exists in the

Fig 66.-Strongylus gigas.-1, female, showing a, the mouth; b, the intestine; c, genital pore; d, anus. 2, cephalic extremity of the male; a, mouth; b, osophagus. 3, caudal extremity of the male; a, cup; b, penis. 4, egg.

kidneys of the horse and the dog, and sometimes in man. It partly destroys this organ, and has been seen a mètre in length. The Strongylus commutatus often lives in great abundance in the lungs of the hare, and the Strongylus filaria in the lungs of the sheep, occasionally in such great numbers that their presence produces pneumonia.

Porpoises generally have strongyli in their lungs and their bronchia, and they are seen by thousands in the

sinus of the Eustachian tube. We collected a large bottle full from a single porpoise around its internal ear. When we consider the prodigious number of these creatures, may we not suppose that they are able to multiply in the organs which they occupy, as well as migrate to infest other individuals.

Different generic and specific names have been given to these Strongyli. A round worm found in the intestines of the dog, the Strongylus trigonocephalus, lives at first in damp earth or mud like the rhabdites in general; it then passes into the dog, and there becomes a sexual Strongylus. It is 2 possible that there are others in the same category.

The Ascaris lumbricoides is a large round worm which attains the size of a quill pen, and which is commonly found in the stomach or the lesser intestines of children when in good health. Aristotle was acquainted with it. It has been observed

throughout Europe, in Fig. 67-Ascaris lumbricoides.-1, com

Central Africa, in Brazil,

plete worm, 2, head, 3, tail of the male,
4, middle of the body of female,

and Australia. The same species lives in the intestines of the pig; but the Ascaris megalocephalus, which is usually found in the horse, is of a different species.

The Ascaris acus of the pike lives at first in a common white fish, the Leuciscus alburnus, and passes with this fish, which serves it as a vehicle, into its final host.

Another common nematode, the Oxyurus vermicularis (Fig. 69), a parasite of man, is a small worm of the size of a fine pin, which often multiplies in the rectum of children, causing intolerable itching. It is by means of their microscopic eggs that they penetrate into the system; these are hatched in the stomach, and are completely developed at the endof eight or ten days. They pass from the anus in great numbers.

Fig. 68.-Trichocephalus of man.-1, female, a, cephalic extremity, b, caudal extremity and anus, c, d, digestive tube and ovary, e, orifice of sexual apparatus. 2, isolated egg. 3, male, a, cephalic extremity, b, anus, c, digestive tube, d, spicula or penis, e, sheath into which it is withdrawn.

Fig. 69.-Oxyurus vermicularis.-1, male of natural size, 2, female, id., 3, cephalic extremity, magnified.

The brood of worms from the eggs of the Ascaris megalocephala of the horse live in freedom, and go through all their phases until their sexual development separately; there are males and females. The

generation which descends from these is distinguished by being of a much smaller size.

The name of Trichocephalus has been given to nematodes which have the cephalic extremity very thin, and ending in such a fine point that it is difficult to discover the mouth. The Trichocephalus of man (Fig. 68) is a curious nematode, which was discovered by a student at Göttingen, in 1761. It is usually found in the cæcum, in which more than a thousand have been met with together. The female is from 40 to 50 millimètres long, the male about 37 millimètres. A female Trichocephalus affinis having laid her eggs in an aquarium, the whole of the contents were introduced into the stomach of a lamb, seven months afterwards, and the walls of its intestines became infested with trichocephali.

No animal at any time has attracted so much attention as that little worm which lives in flesh, rolled up; it is about the size of a millet seed, and was found by chance in the dissecting-room of a London hospital, some forty years ago. The plague and the cholera did not inspire so great fear, and this fright had almost passed from Germany throughout the rest of Europe. We were not among those who wished to take measures at all hazards against the invasion of this worm, since nothing induced us to believe that more trichinæ existed then in Belgium than in ordinary times. These measures would have produced no other effect than uselessly to disturb the minds of the public.

Trichiniasis, which was the name given to the disease caused by these worms, reminds us of tarantism, that is to say, the effects produced by the bite of the tarantula. Mons. Ozanam wrote an interesting work on this subject,