But we have not yet done with the wood-lice. Are these interesting little creatures (they _are_ interesting, are they not?) oviparous or viviparous? I defy you to show me anywhere a single wood-louse's egg. Have the patience to observe our crustaceans more nearly. Among the crowd, you will remark some--they are the females--with a kind of membraneous pouch underneath the body, stretching from the head to the fifth pair of legs. The pellicle which forms this pouch is so thin, and so transparent, that you can distinguish the eggs within it. These eggs, instead of being expelled for incubation, remain in the mother's pouch until they are hatched. At that felicitous moment, the membranous bag splits cross-wise, longitudinally and transversally, to permit the emergence of the young wood-lice. The latter are extremely small, and in form resemble nothing in the world so much as a little white line (Fig. 35, _b_). They differ from their parents only in having one pair of feet, and one ring less than they have. They undergo no metamorphoses. After their birth, the little ones, which have proportionally very large antennæ, do not immediately separate from their mother. By a wonderful act of forethought on the part of Nature,[56] they keep themselves concealed in the middle of the respiratory _laminæ_, which garnish the under part of the tail. The specific characters of the _Oniscus asellus_ are tolerably well defined. By its rings of dark gray, a little lighter at the edges, which form for it an articulated, glossy carapace, marked with white spots, longitudinally arranged; by the uniform pale gray colour of its belly and its legs, covered with scattered hairs; and, particularly, by its habits, our wood-louse, which the Germans call cellar-louse (_Kellerlaus_), is distinguished from its kindred species, of which naturalists have made distinct genera. Thus, the _asellus_ found generally under stones, which counterfeits death by rolling itself up in a ball like a hedgehog, and will rather suffer itself to be crushed than unfold, is the _Oniscus armadillo_, which some naturalists transform into the _Armadillo vulgaris_. (See Fig. 36.) This species prefers the solitude of the field to inhabited places. Its body is considerably expanded, and its rings do not terminate in a point on their lateral and posterior edges. [Illustration: FIG. 36. _Oniscus armadillo._] Another species, equally common underneath stones, has its head and tail covered over with granulations; its antennæ are composed of seven joints, of which the fourth and fifth are perceptibly situated lengthwise. This is the _Oniscus granulatus_ of some entomologists; others have designated it the _Porcellio scaber_. Why not simplify the study of species? The wood-lice seem to live upon decomposed vegetable matter. But in default of other food, they devour their own kind; in this respect resembling beings who are supposed to rank much higher in the animal hierarchy.