The _nervous system_ of the Myriapods consists, as in Insects, of a brain, which may be more or less developed, a circumoesophageal ring embracing the oesophagus, and a ventral chain of ganglia, and in some cases (Newport) of a system of visceral {51}nerves. With the nervous system we may mention the sense organs, the eyes, which are present in most cases, though wanting, as has been already stated, in many groups. They are usually present as clusters of ocelli or eye spots closely packed together, or (in _Scutigera_) as peculiarly formed facetted eyes. The sensory hairs on the antennae must be reckoned as sense organs, as also the tufts of sense hairs on the head of _Polyxenus_. _Scutigera_ has also a peculiar sense organ beneath the head, consisting of a sac opening on the under side of the head full of slender hairs, each of which is connected at its base with a nerve fibre. Except the eyes, the Myriapod sense organs have usually the form of hairs or groups of hairs connected with nerve fibres, which communicate with the central nervous system. [Illustration: FIG. 31.—Under side of the head of _Scutigera coleoptrata_, with sense organ. _eo_, Opening of sense organ to the exterior; _o_, sense organ shown through the chitin; _m_, mouth; _oc_, eye; _mxl_, maxilla; _f_, furrow in the chitin. (Heathcote, Sense organ in _Scutigera coleoptrata_.)] [Illustration: FIG. 32.—Highly magnified section through head of _Polyxenus lagurus_, showing sense organ. _ext.cut_, external cuticle; _t_, tube surrounding base of sense hair; _gang.c_, ganglion cell. (Heathcote, Anatomy of _Polyxenus lagurus_.)] These two sense organs are shown in Figs. 31 and 32. Fig. 31 shows the under side of the head of _Scutigera_ (Fig. 17), with the position of the sense organ and its opening. Fig. 32 is part of a section through the head of _Polyxenus_ with two of the sense hairs. Each spine or sense hair fits into a cup in the chitin of the head; and the lower or internal part, which is divided from the upper or external part by a rim, is joined to a ganglionic nerve cell (_gang.c._). The Myriapods are of separate sexes, and the generative organs in both cases usually have the form of a long unpaired {52}tube, which in the male is connected with accessory glands, and in the female is usually provided with double receptacula seminis. The generative openings usually lie near the base of the second pair of legs (Chilognatha), or at the posterior end of the body (Chilopoda). In the Chilognatha there is usually in the male an external copulatory organ at the base of the seventh pair of legs, remote from the genital opening.