2

3

into two genera, the common' and the grapeheaded tapeworms. The former is the most common in England, but the latter' seems the most gigantic of any. Sir A. Carlisle, who has a most excellent paper upon the former, in the second volume of the Linnean Transactions, says that he has met with them from less than six feet long and consisting only of fifty joints, to thirty feet long with four hundred joints. But these are nothing compared with others of the latter observed by continental writers. Bonnet mentions them as sometimes extending to the length of thirty ells, probably meaning French ells, or one hundred and twenty-five feet, and Boerhaave, one that greatly exceeded that length.

These animals differ little from each other, but in the common tape-worm, the head which has a circular orifice or mouth at its extremity surrounded by a number of rays of a fibrous texture, and probably serving to fix the mouth, has on each side two small suckers which doubtless attach the head more strongly. The mouth, before spoken of, is continued by a short duct into two canals, which pass round every joint of the animal's body conveying its aliment, and sending a transverse canal along its bottom which connects the two lateral ones. Sir Anthony injected upwards of three feet of these

1 Tania.

3 Tænia solium.

2 Botryocephalus. PLATE I. B. FIG. 3.
Botryocephalus latus.

canals by a single push with a small syringe, but he could not make it pass upwards beyond two joints which seemed to indicate the existence of valves opening only in one direction. He says there is no anal orifice, but other authors expressly mention one, and it is not easy to conceive, if the last has no orifice, how the joints can increase in number and remain concatenated. The body is composed of a vast number of joints, each having an organ whereby it attaches itself: those nearest the head are always small and they enlarge gradually as they recede from it. The extremity of the body terminates in a small semi-circular piece.

Sir Anthony suspects that the several joints of the tape-worm are separate animals. This is an old opinion and has been adopted by several zoologists, but Bonnet seems to have proved, that however extended, the tape-worm is only a single animal. Whilst a living head remains attached to some joints, this creature maintains its station and keeps augmenting their number, but when any are broken off, they appear not to form new heads, as Sir Anthony supposes, but die and are expelled from the body. Their nutriment is probably derived from the gastric, pancreatic, and other juices which perpetually flow into the stomach and intestines of the animals they infest; and they employ the tentacular rays as a mean of irritation to determine a greater secretion of these fluids.

It would be an endless labour to expatiate in this vast field where the rest of the animal kingdom is concerned, amidst therefore the various and strange forms that are destined to this office, I shall select only a few, beginning with one that affects one of the most valuable of our animal possessions, I mean the Hydatids,' which particularly and often fatally affect our flocks of sheep, not indeed that they are confined to them, for they are found also in swine, deer, and oxen, and even in man himself.

These animals resemble the tape-worm in their oral organs, but their body, especially posteriorly, is vesicular. The lymphatic vesicles are what medical men call hydatids; they are found usually in the brain and in the liver of these animals. Their size varies according to the species, some are as big as the fist, and one was shewn to the School of Medicine in Paris as big as a man's head. Their shape varies, but generally is somewhat spheroidal, their substance is composed of membranes one on another more or less thick, and formed of circular fibres visible only under a lens; they are half-filled with transparent lymph. They exhibit a peristaltic motion which is often very lively.

Three species more particularly annoy our sheep. The cerebral hydatid, which finds its

way into the brain of these poor animals and occasions the vertigo; and the vervecine' and ovine hydatids,' which penetrate into their lungs and liver and occasion the rot. It is usually discovered when a sheep is infested by the former of these pests by its turning often and briskly its head on one side; when it runs very quick, and suddenly stops without any apparent cause; in a word, when it appears almost deranged. Though the progress of the disease they produce is slow, it is generally fatal. Five hundred have been counted in the head of a single sheep. The ravages, however, produced by this hydatid are nothing to those occasioned by the other two, which attack the lungs and liver and cause the rot, by which, in some years, thousands perish.

Some worms are remarkable for their very singular forms or station. One that attaches itself to the gills of the bream, looks like a double animal,' and a kind of fluke,* in great numbers infests the ball of the eyes of the perch."

Though at first view the animals of which I have in the present chapter given some account seem to be altogether punitive, and intended as scourges of sinful man both in his own person and

1 H. vervecina.

3 Diplozoon paradoxum.
4 Diplostomum volvens.
5 Ibid, FIG. 6.

2 H. ovilla.
PLATE I. B. FIG. 4.
Ibid, FIG. 5.

in his property, and their great object is hastening the execution of the sublapsarian sentence of death, yet this evil is not unmixed with good. Though fearful and hurtful to individuals, yet it promotes the general welfare by helping to reduce within due limits the numbers of man and beast. Besides, with regard to the Lord of the Creation, these things are trials that exercise his patience and other virtues, or tend to produce his reformation, and finally to secure to him an entrance into an immutable and eternal state of felicity, when that of probation is at an end, so that the gates of Death may be to him the gates of PEACE and REST.

CHAPTER XII.

Functions and Instincts. Annelidans.

THE animals we have just been considering form an almost insulated group, so that it seems not easy to say to what tribe they are most nearly related, but the soft Pseudo-leeches, as was observed above, especially those that have rudimental tentacles, seem to tend somewhat towards the molluscan tribes; they exhibit considerable resemblance to the blood-suckers or true leeches, and like them have an instrument