[Illustration: FIG. 33.—Mouth parts of _Chilognatha_. (From C. L. Koch, _System der Myriapoden_.) _f_ and _g_, The mandibles. The parts marked _a_, _b_, _c_, _d_, _e_ are firmly united and constitute the broad plate No. 3. They have received the following names—_a_, _b_, Internal stipes; _c_, external stipes; _d_, malellae; _e_, hypostoma.] After the mouth parts we come to the legs. We first notice the fact that the bases of the legs in each pair are closely approached to one another. They are so set into the body that the basal joints, or, as they are called, the coxal joints, nearly touch. This is the case in almost all Chilognatha, except in the Polyxenidae, and it is a fact connected with some important features in the internal anatomy. Then we have the peculiarity in the Chilognatha which has formed the basis of most classifications which have placed these animals in a group by themselves. This is the possession in most segments of two pairs of legs. This characteristic has caused the group to be called by some naturalists Diplopoda. As a general rule, the first four segments {54}have only three pairs of legs between them, one of them being without a pair of legs. This legless or apodal segment is usually the third. From the fifth segment to the end of the body all the segments have two pairs of legs each. The legs are shorter than those of the Chilopods, and are all nearly equal in size. This is not the case in the other Orders. The legs are commonly wanting in the seventh segment of the male, and are replaced by a copulatory organ. This peculiarity is related to the different position of the generative openings in the Chilognatha. Another anatomical feature peculiar to the Chilognatha is the possession of the stink glands—the _glandulae odoriferae_ before mentioned. This, however, is a character which does not hold for all the Chilognatha, since the Polyxenidae have none of these glands. All the other families, however, possess them, and they are present in none of the other Orders. As regards the internal anatomy of the Chilognatha, the _digestive canal_ differs mainly in the glands which supply it with secretions. It receives the saliva from two long tubular salivary glands, which open at the base of the four-lobed plate which has been mentioned as the third of the mouth appendages. The secretion of these glands is used, as has already been said, in the process of preparing the nest for the eggs. We cannot fail to be reminded of a similar function of salivary glands in those swallows, which prepare the nests of which bird's-nest soup is made with the secretion of the salivary glands. Another feature in the form of the digestive tube is that in many cases, if not in all, it is marked with constrictions which correspond with the segments of the body.