These cocoons, when opened, were found to contain about a hundred eggs. Lyonnet kept them in water till the eggs hatched. “The larvæ,” he says, when this had taken place, “remained one day enclosed in the cocoon before escaping. Then they made an oval aperture in the lower part of the flattened end of the cocoon, and escaped through this into the water.”[143] Here they fed upon snails, their manner of eating which is thus described: “The larva seizes the snail with its mandibles, then bends its body backwards and rests the snail upon the broad back, which serves as a table (as with the larva of the grain-eating ant of Texas). In this position, holding the snail in its legs, the larva breaks the shell, and devours it.”[143] When full-fed the larvæ left the water, and one of them was placed by Lyonnet in a box full of moistened earth. This it entered, and, some days afterwards, changed into a large white pupa or chrysalis, about which there was one curious feature, viz. that “on each side of the head”—or, as an entomologist would say nowadays, “on the fore part of the prothorax—were three brown, strong hooks. Two others of the same kind were found at the hinder end of the body.”[143] These hooks were solid, so that they could contain no part of the perfect insect, and Lyonnet points to them as good examples of _apparently_ useless structures. Their office, indeed, he himself knows, but he does not reveal it till the usual philosopher has been imagined who denies that they can have any. Then, of course, comes the anticipated discomfiture of this unwary person—so frequent in the eighteenth century—who, unwarned by experience, has walked quietly into the trap. “In the damp earth which the pupa requires the above-described hooks fulfil a purpose, unexpected by us, but, at the same time, of great importance. The skin of the pupa is very delicate. Lying on damp earth, it could hardly escape injury, and the weight of the body might easily give it a distorted shape. But (_Monsieur le Philosophe_) the pupa protects itself from these dangers by assuming an unusual attitude. It extends itself back downwards in a horizontal position, and supports the weight of its body by the three sets of hooks, as upon a tripod. In this attitude, though surrounded on all sides by moist earth, it keeps its body from actual contact with any object until it has assumed its final shape. Thus,” continues Lyonnet, turning full upon the stupefied philosopher, “we see how necessary are those hooks, which at first sight appeared so useless. To decide that this or that structure is superfluous because we cannot guess its use is truly ridiculous in beings whose information is so limited as ours.”[143] Applauding shouts (“_Mais certainement!_” “_C’est vrai cela!_”) rend the air, and the imaginary philosopher goes out in a state of painful confusion.