Nervous system.—The nervous system of the Myriapoda, as in all the Articulata, exhibits a double series of ganglia connected by cords of inter-communication. Tile supra-cesophageal ganglion, situated within the cephalic segment of the body as relates to its development, seems to hold a place intermediate between that of the Annelida and of Insects, or perhaps more strictly speaking, corresponds with the larva condition of the latter. The ventral chain of ganglia is numerous in proportion to the number of segments which enter into the com position of the body, their number decreasing as the locomotive limbs over which they preside become more fully developed and capable of more vigorous action. Thus in Julus and Geophilus, where the limbs are extremely numerous and feeble, the ganglia in their num ber and small size approximate the condition they exhibit in the I\ereis or more elevated Annelides, but in Scolopendra (fr. 313) the more powerful limbs and stronger muscles required by their carnivorous habits demand greater developemeut of the centres of the ner vous system.
resemble Insect larva' that little can be said concerning them in addition to what the reader will find elsewhere stated. (See articles AN NELIDA, CRUSTACEA, ARAGIINIDA, INSECTA.) The antenna upon the head, which are in variably two in number, correspond in all essential circumstances with those met with in Insects, and doubtless perform the same func tions. The eyes when present, which is not the case in all the genera, exhibit the form of simple ocelli congregated upon the head, and arranged in lines or triangular patches ; but in no case do they exhibit the appearance of a really compound eye, such as is possessed by the generality of Insects in their perfect state. With respect to the other. senses, touch, taste, and smell, but little is known except by conjec ture, and presuming them to exist we can only suppose them to be conferred in the same manner as in the real Insect.
Generative remarkable difference exists between the Chilognatha and the Scolo pendroid Centipedes with respect to the posi tion of the organs of generation. In the former the external openings, both of the male and female genitals, are situated near anterior extremity of the body, as is the case among the Annelida; whilst in the Chilopodous genera, which exhibit a higher grade of organi zation, the generative apertures are found in the caudal segment as in the Insects.
In Lithobius the structure of these parts is in both sexes very simple. In the male there are three long and convoluted secreting tubes resembling the simplest form of the testis in Insects, wherein, doubtless, the seminal fluid is elaborated. These are united at their termi nations so as to form a kind of common recep tacle, front which two tubes proceed to the root of the intromittent organ, at which point they are joined by four smaller auxiliary vessels, which seem to take their origin in masses of fatty substance. The penis is a horny cylin drical tube that can be protruded from beneath a valvular plate which covers the anal orifice (fig. 309, o).
The female apparatus consists of a single sacculated ovarium, occupying the mesian line of the body. From this proceeds a narrow excretory duct, which, however, prior to its termination beneath the anal segment becomes considerably dilated into a cavity that has been improperly named uterus. Here it receives two sets of supplementary vessels, the one a pair of wide caeca, the other composed of four convoluted vessels apparently destined to secrete some additional covering to the eggs before their extrusion. The female generative orifice, situated in the anal segment, is covered with a horny plate and furnished with a pair of small horny forceps calculated to assist hi copulation.
The male generative organs of Scolopendra present a very peculiar structure ; but these we have already described elsewhere (see GE NERATION, ORGANS OF).
The male generative organs of Julus (fig. 314, A) are two elongated and partially convoluted tubes placed side by side beneath the alimentary canal immediately above the nervous system.
The excretory ducts or terminations of these tubes run towards the anterior part of the body, where they terminate in two organs of intro mission (a), which pass out at the under surface of the seventh ment by distinct fices behind the venth pair of legs. Posteriorly they tend backwards as far at the middle of the colon. In the rior third of their course they lie close together, but wards separate, come smaller, and have developed from their sides at short distances a number of minute glandular caeca, or transparent vesicles (r), which doubtless constitute the secreting portions of the apparatus or proper testes of the animal.
The two efferent ducts, whereby the secretion of these caeca is conveyed out of the body, inter-communicate freely by short transverse canals (fig. 13, d d), and from the sacculated appearance that they present towards their termi nation appear in some species to perform likewise the office of reservcirs for the seminal fluid. In a large African species Mr. Newport found the double organ of intromission to be prehensile (fig. 314, B, a), each part having the form of a distinct claw between the move able joints, of which passes out the elongated half corneous penis. These parts are co vered in anteriorly by a horny valve somewhat of a trian gular form, and the whole oc cupies an oval space on the under surface of the seventh segment, corresponding to that usually occupied by the ley. " With regard to the product of secretion in these organs," ob serves Mr. Newport, " I have never yet found any thing but a granulous fluid in the caeca, apparently similar to the gra nules in the higher animals from which Spermatozoa are produced, but this might have arisen from the immature re cent specimens I was alone able to obtain. It would be interesting to ascertain whether these germs of Spermatozoa are produced in the caeca as there seems reason to believe, as we shall presently find that the ova in the female are secreted in sacs which appear to be ana logous to these caeca in the male organs. I am inclined to think that the Spermatozoa are not developed until the granu lous fluid has passed into the efferential ducts at the season of impregnation." The female organs of the Julidx (fig. 315) are described with equal minuteness in the paper above referred to, from which we extract the following exceedingly valuable observa• Lions, as nearly as possible it the words of Mr. Newport hitm self, to whom we are also in debied for the illustrative fs gures. In the female Julus, tin organs of reproduction are a; simple as those of the male They consist of a single don gated bag or oviduct, coverec on its exterior surface with very great number of ovisac, or coeca of various sizes, eacl of which secretes but a sing!, ovum. This oviduct extend backwards beneath the alimentary canal, from its double vaginal outlet (a a), which is situated in the fourth segment behind the second pair of legs, as far as the posterior part of the rectum close to the anus, where it ends in a cul-de-sac (d). It is most nearly in contact with the alimentary canal on its upper surface, but is separated from it by adipose tissue; in the pregnant female it is smooth, and dis tended with ova that have passed into it from the ovisacs, and are ready to be de posited immediately after intercourse with the male. The ova at the anal extremity, that is, at the commencement, of the duct are as perfect as those near the vaginal outlets. The oviduct contains within its cavity, at least from seventy to eighty of these perfect eggs awaiting impregnation, arranged in two or more irregular rows, and greatly distending its sides. In some of the larger species of the genus there are four and in others five rows of eggs, the number of which is much greater than in our na tive species. The ovisacs (fig.315 and 316,c e) are little sacculi, distributed thickly to the num ber of many hundreds over the whole exterior of the oviduct, from its posterior or meal ex tremity to within a short distance of its vaginal outlets. Each ovisac, whatever be its state of developement, contains but a single ovum, every part of which is produced in it, from the germinal vesicle in the most rudimentary form to the yelk, albuminous fluid, and shell. This fact deserves particular consideration. A large proportion of the ova in the ovisacs er arrive at maturity, but are retarded in their growth by the more rapid developement of others that are near them, so that on examining an oviduct partially distended with ova, the greater number of ovisacs in different states of developement, are at the sides and on the under-surface of the duct, in parts which corres pond to the interstices between the fully deve loped eggs, that have passed into the oviduct, or are still forming on its exterior. One row of ovisacs usually exists on each side of the duct near its upper part, but most of the ovisacs ui the course of development are at its sides.