the free end of the egg, the other remaining still attached to the leaf.

When, in a former letter, I spoke of the peacock and the crocodile, had I stated that the egg, when hatched, produced a young crocodile in the first instance, but that this afterwards changed into a peacock, you would justly have considered that statement as resting on no better authority than a fable from Ovid's Metamorphoses. Yet, in many instances, we find in insects metamorphoses as extraordinary in appearance as that would have been; this, however, will not apply to our butterfly so strikingly as it would to various other insects, as the dragon-flies, water-beetles, and many more; and yet even here there is sufficient cause for admiration. When the egg is hatched, does a little butterfly proceed from it? No; but a creature very different in appearance, a crawling worm, or, in other words, a caterpillar. The young caterpillar feeds on the leaf of the cabbage, and in a short time grows to some hundred times its original bulk. About the end of June it has acquired its full growth; and then, influenced by that invisible guide whose operations are so conspicuously evident in the insect kingdom, it leaves the plant which can

the shelter of some tree or wall, it climbs to a certain height, fixes itself in a perpendicular direction, casts its skin, which it had done several times before, and in a few hours is changed into the chrysalis (fig. 3. d.), being altered

a, the cabbage butterfly; b, its eggs; c, caterpillar; d, chrysalis ; e, egg magnified.

almost as much in appearance from the caterpillar as either is from the butterfly. This chrysalis is attached by several silken cords which pass across the thorax, and by this means it is secured from the chance of falling during the period of its sleep. In this state it remains about sixteen days, and then bursts from its

case, the complete butterfly. Should the egg be hatched late in summer, so that the chrysalis is not completed till towards the end of September, then it remains all winter, and the butterfly appears in the ensuing spring.

Insects, from the time they leave the egg till they assume the chrysalid state, are named larvæ, but many of these have forms very different from that of the caterpillar or larva of the butterfly; and such is the caddis worm. This is the larva of what is commonly called the May-fly, often the water-fly; but many species, and some even belonging to different genera, go under these denominations. Without, however, attending to species, it is sufficient at present for us to consider the caddis or cadew worm simply in relation to its general history. The generic name of the perfect insect is Phryganea, and the larvæ are well known from their practice of forming cases of extraneous bodies, in which they enclose and protect themselves. You have often, in streamlets and pools, observed bits of straw as it were, or fragments of wood moving at the bottom: these are the cases I allude to.

The larva of the phryganea is a long jointed worm, furnished on the fore part of the body

part of the animal, are enveloped by a firm crust, like the skin or covering of a beetle, though not so strong; but the hinder parts of the body are quite soft and unprotected (fig. 4. a.). I may remark, that we have examples of other animals being partly enveloped in a strong crust or coat of mail, while the rest of the body is covered merely by a soft skin; such are the Hermit-crabs-one species of which, Cancer Bernhardus, or Bernard the Hermit, is common on many of our shores, and is vulgarly considered as a young lobster. To protect the naked part of his body, he takes possession of some empty shell, and retreats into it, tail foremost, and there is secure from the attacks of enemies which otherwise might sorely annoy him. As the crab grows in size, his house, of course, becomes too small, and he has then to search for a larger; which being found, he leaves the old, and takes possession of the new dwelling, till he is again obliged to make another flitting to gain further accommodation.

The larva of the phryganea has a different mode of proceeding. One might suppose it next to an impossibility that an animal resident in water could spin a thread, and that a strong one, or that it could form for itself an envelope not unlike a mantle of silk; yet such is the

case and there are animals living in water which can spin threads more durable and strong perhaps than is done by any on land, the silkworm not excepted. You know the common muscle; it spins threads of remarkable strength,and why?—that it may moor itself to the rocks and other substances, and thereby save itself from being cast ashore by the violence of the waves; and of these cables the animal can spin many hundreds, though it proportions their number to the risk of shipwreck to which it may be exposed. When subjected to the violence of a turbulent sea, it increases the number, and when in secure and sheltered spots it makes them less numerous; yet how many people have been acquainted with the muscle all their lives, and with its beard (for that is the name given to its mooring apparatus), without ever for a moment thinking on the subject!

As illustrative of this property of the muscle, I may mention, that its aid has been called in to assist in securing by its cables even works of human construction. At the town of Biddeford, in Devonshire, there is a long bridge of twentyfour arches across the Towridge river, near its junction with the Taw. At this bridge the tide flows so rapidly that it cannot be kept in repair by mortar. "The corporation, therefore, keep