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. 剩 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.5 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 1 H. vervecina. 3 Diplozoon paradoxum. 2 H. ovilla. Ibid, FIG. 5. and 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 of suction, though employed, perhaps, in extracting the sap or the blood of plants, and at the same time, in many respects, as we have lately seen, they approach the polypes. The Flukes, likewise, appear to have some characters in common with the leech,1 so that a passage is open from the intestinal worms towards the Annelidans, some of which, as the earth-worm, occasionally become intestinal, and several are possessed of reproductive powers almost as great as those of the pseudo-leech, or the polype. I shall therefore next, in taking my departure from the worms, bend my steps to the animals just mentioned, which formerly bore the same general denomination. They are called Annelidans, I suppose, because they appear to be divided into little rings, or else to have annular folds, and are soft vermiform animals, some naked, others inhabiting tubes, in some simply membranous, in others covered with agglutinated particles of sand, and in others formed, like those of the Molluscans, of shelly matter. Some have neither head, eyes, nor antennæ, while others are gifted with all these organs; instead of jointed legs, their locomotions are accomplished by means of fleshy bristle-bearing retractile protuberances or spurious legs disposed in See above, p. 325. lateral rows. Their mouth is terminal but not formed on one type; in some it is simple, orbicular or labiated; in others it consists of a proboscis often having maxillæ. They have a knotty spinal marrow, in this being superior to the Molluscans and approaching the Condylopes. They have red blood, and their circulation is by arteries and veins, but they have no special organ for the maintenance of the systole and diastole, their Creator not having given them a heart, but where the veins and the arteries meet, there is an enlargement, and the systole and diastole is more visible, as Cuvier remarks, than in the rest of the system, these enlargements therefore seem to represent a heart. Savigny, in the third part of his Systême des Animaux sans Vertèbres divides them into five Orders, of which he gives only the characters of the four first, intending to publish, in a supplement, his account of the fifth; these Orders he arranges in two Divisions-the first including those that have bristles for locomotion, and the second those that have them not. 1. His first Order he denominates Nereideans, and characterizes them as having legs provided with retractile subulate bristles, without claws; a distinct head with eyes and antennæ; a pro 1 Nereidea. boscis that can be protruded, generally armed with maxillæ. 2. The second he names Serpuleans, these add to the legs of the former retractile bristles, with claws; they have no head furnished with eyes and antennæ, and no proboscis.' 3. The third he names Lumbricinans; these have no projecting legs; but are furnished with bristles seldom retractile; they have no head with eyes and antennæ, and no maxillæ. 4. His fourth Order he names Hirudineans. They have a prehensile cavity, or sucker, at each extremity, and eyes. 5. In his fifth Order he intends to comprehend those Annelidans that have neither bristles nor prehensile cavities, but his account of this has not been published. He begins with the most perfect of the Annelidans, but viewing them in connection with the worms I must reverse the order, and instead of descending ascend, which will bring me ultimately into connection with the more distinctly jointed animals the Condylopes. 1. The Order of Hirudineans includes animals that are of the first importance, as well as some that are fearfully annoying, to mankind. The common leech3 has long been so much in request 1 Serpuleæ. |