In the innocent butterfly, who lives on the juice of flowers, the digestive tube terminates externally in a sort of trunk, twisted in several convolutions, which is nothing more than an exaggerated elongation of the two jaws, which become hollow within, and form a tube when joined together. When the insect alights on a flower, he suddenly unrolls this trunk, and sucks in the juices from the depth of its "corolla," as you would drink up liquid with a straw from the bottom of a small vial. Amuse yourself some summer's day by watching a butterfly in his labors amongst the flowers: sometimes he stops still, but oftener he is contented to hover over them; and, as he does so, you will see a little loose thread, as it were, move backwards and forwards as fast as possible: this is his trunk, which he darts out, while flying, into the corolla of the flowers, but which scarcely seems to touch them, so delicate is its approach.

Less inoffensive far is the trunk of the mosquito-gnat, and of all the detestable troop of blood-sucking flies. It is always a tube; but this tube is no longer a simple straw, but a sheath furnished with stilettos of such exquisite delicacy and temper, that nothing is comparable to them; and these, as they play up and down, pierce the skin of the victim, like the lancets of the lamprey, and, like them, draw in blood as they retreat.

Finally, amongst the parasites, the last and lowest group of insects, the stiletto-sheath is reduced to the size of a kind of little tube-shaped beak, which, when not in use, folds down like the fangs of the rattlesnake.

You do not know, perhaps, what a parasite is. The word comes from the Greek, and significs literally, "that which moves round the corn.' The Greeks applied it to those shameless paupers who, to escape honest labor, made their way into the houses of the great, and enjoyed

themselves at their expense. These parasites are little animals which settle themselves on large ones, to suck in, without having worked for it, the blood which the others have manufactured. The wolf hunts, fights, and tears its victim in pieces; and then, by means of that interior labor which I have spent so much time in describing, transforms it into nourishing liquid: and when all this is accomplished, the little flea, who lives hidden among his hairs, coolly draws out for his own use the valuable blood obtained with so much effort. There are many parasites in the world, my dear child-yourself, for instance, to begin with—who are perfectly happy to chew your bread without asking where the corn comes from which made it. But you have heart enough to see plainly that this indifference ought not to last, and that it is not honorable to go on living in this indefinite manner at other people's cost only.

You will some day have duties to fulfil, which you should accustom yourself to think of now, in order that you may prepare yourself for them beforehand, so that it may never hereafter be said of you that you passed through the midst of human society, taking from it all you needed, without giving it back anything in return. I advise you to conjure up this idea when the time comes to leave off playing and begin preparing to be of use. The sort of thing is not always very amusing, I admit, but you must look upon it as the ladder by which you will be enabled to rise from the degradation of a parasitical life. If you were in a well, and some one were to let down a real ladder for you to get up by, I do not think you would complain of the difficulty of using it. It is for you, then, to consider whether you would like to remain for ever in your present condition; for those who learn nothing, who submit to nothing, who are good

for nothing, but to show off and amuse themselvesthese remain parasites all their lives in reality, however little they may sometimes seem to suspect it.

At your age, however, there is still no disgrace in the matter. God shows us by the insects that little things arc allowed to be parasitical; but on this subject I must return to a point in the history of animals which I touched upon before. I told you, in speaking of the crocodile, that the perfect state of the inferior animals is found represented in the infancy or less perfect state of those above them and I may say the same again with regard to insects. All the young of the mammalia begin life as parasites, at least, as sucking animals: for they all live at first on their mother's milk, which is nothing more than blood in a peculiar state. But the name of parasite among insects is generally confined to those which take up their abode on the bodies of their hosts; though in common justice it might equally well be applied to the gnat and his relations, who, when once full, make their bow and are off, like the kitten when he has finished sucking. Well, without meaning to find fault, if we descend to the lower ranks of the mammals, we shall find among them many parasites in the received. sense of the word. You remember the pouch to which the marsupials owe their odd name. The young kangaroo remains hidden for months in the pouch of its mother, feeding continually all the time; and it is then a strict parasite. During the four following months it goes in and out, and strolls about between meals, like other young ones of its class, and is then an animal at nurse affording thus a twofold example of the tendency of the great Creator to repeat Himself in His conceptions, here using for the infancy of the mammal the system invented for adult insects-elsewhere repeating the but

terfly in the humming-bird, who may fairly be called a vertebrated butterfly, and reproducing the gnat in the vampire-bat, which I look upon as an enlarged and perfected revise of the original pattern, whence comes the scourge of our sweet summer nights.

And now, surely, I have said enough about these parasites, whose very name, I suspect, will make you shudder after my impertinent application of it. Never mind it depends entirely upon yourself to get rid of whatever you find humiliating in the position I have hinted at. Do all you can to bring happiness to the parents on whom you live at present, and who give their life-blood so willingly for your good. God has made you very different from those little animals who have neither heart nor reason to guide them. Do not be like them, then, in conduct. By a little obedience and love-child as you are you can pay them back what you owe, and they will never complain of the bargain.

LETTER XXXVIII.

CRUSTACEA-MOLLUSCA.

(Crustaceans and Mollusks.)

Crustaceans.

CRUSTACEANS Consist of cray-fish, crabs, lobsters, and prawns, who may be considered cousins-german of insects, among which more than one naturalist has thought they ought to be placed. Like them they are divided into grinders, having the same action of the mandibles; and suckers, who are also parasites, and have tubular sheaths containing stilettos. Mammals and birds are the vic tims of parasitical insects; fishes have been reserved for the crustaceans, who do not disdain also to fasten upon their humble neighbors, the mollusks; and even among themselves the little ones settle down on the great. A few live on land, but an immense majority in water, and seem destined to represent, in the aquatic world, the aerial class of insects, from whom, however, they differ in many ways.

The first difference is in that stony crust with which they are enveloped, like the cockchafer in his horny cuirass, and which you must know well enough if you have ever eaten lobster. Wherever we meet with horn in insects, we find stone in crustaceans. stony, and the teeth of the stomach also. structed on the same plan, only the changed.

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The jaws are

They are conmaterials are

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