The last Spider which we can here notice is the little Hunter (Salticus scenicus), which, in its zebra-like marking of black and white bands, is frequently seen leaping on window-sills and garden-fences, in the burning sun of summer. Its manners cannot be better described than in the words of old Evelyn :-"Such I did frequently observe at Rome, which, espying a fly at three or four yards' distance upon the balcony where I stood, would not make directly to her, but crawl under the rail, till, being arrived to the antipodes, it would steal up, seldom missing its aim; but if it chanced to want anything of being perfectly opposite, would at first peep, immediately slide down again, till, taking better notice, it would come the next time exactly upon the fly's back. But if this happened not to be within a competent leap, then would this insect move so softly, as the very shadow of the gnomon seemed not to be more imperceptible, unless the fly moved; and then would the spider move also in the same proportion, keeping that just time with her motion, as if the same soul had animated both these little bodies ; and whether it were forwards, backwards, or to either side, without at all turning her body, like a well-managed horse. If, however, the capricious fly took wing and pitched upon another place behind our huntress, then would the spider whirl its body so nimbly about as nothing could be imagined more swift; by which means she always kept the head towards her prey, though, to appearance, as immoveable as if it had been a nail driven into the wood, till, by that indiscernible progress (being arrived within the sphere of her reach,) she made a fatal leap, swift as lightning, upon the fly, catching him in the poll, where

she never quitted hold till her belly was full, and then dragged the remainder home." *

There are several hideous forms of the group in tropical climates, of which the best known is that of the Scorpions. It is impossible to look on one of these, and not be reminded of a lobster-the great palps, with stout dilated pincers, resembling closely the claws of that much more. respectable crustacean. The Scorpions are widely scattered; several are found in the south of Europe, but it is in the tropics that they most abound. The Scorpio afer of the East Indies grows to six inches in length, and its sting is rather a formidable affair. We once experienced the effects of a West Indian Scorpion's venom, which were, however, not more severe than those of a wasp's or bee's sting. The weapon is a hooked, very acute joint at the extremity of a six-knobbed tail, within which is a bag of subtile poison, infused into the wound through two minute slits near the point. These animals lurk under stones and in dark crevices, living on beetles and other insects, which they catch with their claws. Tiny species closely resembling them, except that the tail and the sting are wanting, are common in old books and papers, and sometimes parasitically infesting insects. These constitute the genus Chelifer, and form the connecting link between the Scorpions and the Harvest-men or Shepherdspiders (Phalangium), which are so common in autumn, remarkable for the great slenderness and length of their many-jointed legs, which continue to move a long time after being separated from the body.

The tribe of Mites comprises small and generally very

* "Travels in Italy."

N

minute animals. Scarlet is their favourite livery, and it often has the appearance of satin or velvet. The Watermites (Hydrachna) are merry little creatures that scuttle along through the water of our pools, looking like tiny globules of red sealing-wax. The Cheese-mite (Siro domesticus) is so common, that possibly, gentle reader, you may have emulated the feats of Samson, slaying thousands at a time, and that with a jaw-bone. If you are fond of dogs or of cattle, you have also, doubtless, made the acquaintance of a vile creature called a Tick (Ixodes), which attaches itself to the poor brutes in some spot inaccessible to their efforts-such as behind the ears, or at the root of the tail-and then, plunging a beak of sharp horny lancets into the flesh, sucks the blood, till its own body is gorged and swollen from the size of a hemp-seed to that of a horse-bean, when it drops off to make room for another bloodthirsty sucker. And, finally, some of these creatures (Sarcoptes) of minute dimensions, burrowing beneath the skin, become the cause of certain highly infectious cutaneous diseases, which are unhappily too common where cleanliness is neglected.

CHAPTER XXI.

ROTIFERA (Wheel-bearers).

NEARLY two centuries ago, a great impetus was given to physical science by the application of the newly-invented Microscope to substances so minute, that their forms, or at least their structure, could scarcely be appreciated by the unassisted sense. The waters were found to be teeming with living creatures of multitudinous kinds, constituting what might be called a new world of life. The excessive minuteness of these creatures being their most obvious character, and the imperfection of the instruments as yet in use permitting no more than a vague perception of their exterior figure, it was natural that they should be associated in one group, under the term Animalcules.

More precise observation has, however, determined that, among these minute forms, are comprised animals of very various grades of organisation. Some are the simplest creatures known, as the Monads, of which we treated in the first chapter of this volume; some are not animals at all, but plants of a very low grade, endowed with animal-like powers of locomotion; some are the larvæ of INSECTS; some are minute ANNELIDA and CRUSTACEA; and a considerable number, of high interest from their beauty, their sprightly motions, their perfect transparency,

and their comparatively complex structure, constitute a peculiar class of themselves, under the title of ROTIFERA.

The relation which this group bears to other recognised classes of animals, has been a matter of some debate. It seems generally admitted that they come into the Annulose Division; and we are inclined to place them above the ANNELIDA, having relations both with INSECTA and CRUSTACEA, and forming a link by which the lowest forms of these highly-organised creatures are linked with the highest INFUSOoria.

The earliest known species is one of the most abundant; and though it is not so typical of the class as many others, being one of the lowest forms in organisation, yet as it exhibits, with peculiar clearness, the characteristic. movement which has given a name both to itself and its class, it is popularly considered as the representative of the whole. We allude to the common Wheel-animalcule (Rotifer vulgaris), which is found in most collections of fresh water, and in vegetable infusions that have stood exposed for a few days.

The form of this tiny creature, which does not exceed th of an inch in length, is spindle-shaped or barrelshaped, the lower part tapering to a slender foot, of many joints, capable of being sheathed, telescope-fashion, one within another, and the upper part expanding into two circular disks set with vibrating cilia. It is the motions of these cilia which are so peculiar and characteristic of the whole class; they immediately arrest the attention of the observer, who is struck with wonder to behold what appear to be the dark teeth of two cogged-wheels, set side by side horizontally, and running rapidly round with the