In front of its first ring (a transversal segment) you see a little black head, with two lateral bead-like eyes, and a couple of antennæ. The latter are each composed of three joints, which are extremely mobile; their base is covered by the edges of the sloping head. The most conspicuous rings of the body are seven in number; their lateral borders are pointed in front, and rounded behind. But, if you look closely, you will see some other rings, a little less projecting than the former; they circumscribe the abdominal region, the belly, properly so called, in which the intestines are lodged. These rings, or abdominal segments, are six in number; but they have not all the same form. The one which occupies the tail is triangular, pointed, and surrounded by four (caudal) appendages. The three next segments, counting from the front to the rear, are prolonged laterally in a very marked manner; the two anterior, on the contrary, have no such distinction. As for the caudal appendages, the two outer ones are very strong, conical, and composed of two articulations, while the inner, situated above the former, are frail, cylindrical, and terminated by a tuft of hairs, whence issues a viscous liquid. (See Fig. 35, _a_.) [Illustration: FIG. 35. The Wood-Louse.] An enumeration of these characteristics is tedious, but necessary for the determination of the genus and the species. They belong to the _Oniscus asellus_, or common wood-louse. But why, you ask, why such a strange conjunction of names,--one Greek, ὀνίσκος, the other Latin, _asellus_? Both carry the same meaning: why not, then, have called our tiny crustacean an ass-ass (if such a compound be possible)? Why, neither close at hand nor at a distance, has it the slightest resemblance to an ass; and to say that we have only borrowed these names from the ancients, is neither an explanation nor a justification.