Dissected so as to show its digestive, nervous, and reproductive apparatus; the 'fat body,' and a considerable portion of the dorsal integument having been removed.
Plate VIII. Cockroach, Periplaneta orientalis.
Of the external organs are seen the multi-articulate antennae, the segmented anal appendages or 'cerci,' the compound eyes, portions of the epicranium, of the terga, of the pro-, meso-, and meta-thorax, and of the eight terga of the abdominal somites; and finally, the three pairs of legs articulated to the thoracic somites, and consisting each of a proximal segment known as the coxa; a second and much smaller segment, distinct in these, though not in the saltatorial Orthoptera, from the coxa, and known as the trochanter; a third, the femur, beset below with spines; a fourth, the tibia, more richly armed with spines than the femur; and the fifth, the tarsus, which is quinque-articulate.
a. Antennae consisting of three elongated basal segments, and a multiarticulate appendage made up of as many as ninety-two joints.
b. 1, b. 2, b. 3. Tibiae, sub-quadrangular in shape, and beset along their two narrower sides with spines.
c. 'Cerci anales,' consisting of twelve segments, the terminal one conical, the others thickly beset with hairs. As sexual characters may be noted the absence of the sub-anal styles possessed by the male, and the median emargination of the supra-anal dorsal plate with which the cerci articulate. The cerci perhaps represent a pair of abdominal limbs. They are commonly found in Orthoptera, Pseudo-Neuroptera, and all Thysanura.
d. Nerve ganglion developed upon the nervus recurrens, and seen to give off a nerve on either side, which passes backwards upon the crop to the gizzard and has itself fusiform dilatations of a ganglionic character developed upon it.
e. Common duct communicating with the two lobes of the dendritic salivary gland. The ducts of the two salivary glands fuse mesially with each other, in the angle formed by the convergence and fusion of the ducts of the two salivary bladders or reservoirs with which they fuse in turn, so that the compound duct finds an outlet into the mouth by means of a short common canal. The figure does not accurately reproduce this arrangement, which cannot be demonstrated to the unassisted eye.
f Salivary bladder.
g. Gizzard communicating with the chylific stomach, z, through the intermediation of a short segment of small calibre.
h. Whorl of eight caeca at the commencement of the chylific stomach.
i. Chylific stomach, smooth externally as is the upper half of the homologous segment in Gryllotalpa.
j. Malpighian tubules, in number from twenty-four to thirty; inserted in a zone around the lower end of the chylific stomach. This insertion is unusual, and they generally open into the commencement of the intestine, from which they are developed as outgrowths in Blatta germanica and all Insecta.
k. First portion of the intestine or 'small' intestine.
l. Large intestine or colon; found ordinarily in its upper part distended with the refuse of the ingesta, and below of smaller calibre, and corrugated so as to present a beaded appearance.
m. Rectum showing the longitudinal lines formed by internal ridges supplied with numerous tracheae. The ridges thus developed upon the rectum constitute in the larvae of the Libellulidae, together with a valvular apparatus developed from the caudal tegumentary skeleton, their aerating organ.
n. First abdominal ganglion, closely approximated to the third thoracic, and placed at a slightly greater distance from the second abdominal ganglion. The sixth abdominal ganglion should have been drawn as somewhat heart-shaped, but laterally constricted so as to have the appearance of being made up, as it probably is, of more than one distinct ganglion. The two oviducts pass to their point of fusion from the outside of the angle bounded by the nerves, seen to spring from this ganglion. The sub-oesophageal ganglion is not seen in this figure, being, as always in Insects, in such close apposition to the supra-oesophageal or cerebroid ganglion, as to have been sometimes, but inconveniently, described as making up, together with it, a 'brain.' Counting, however, this ganglion whence the mandibles, maxillae, and labium receive their nerve supply, we find that the entire ventral cord is made up of nine ganglia, the last of which may be taken as representing more than one ganglion.
o. 'Verticillate' ovary of right side, consisting of eight egg-tubes, connected by a suspensory ligament, which is made up by the fusion of filaments from their respective apices, and is attached to the dorsal region of the thorax. The proximal extremities of the oviducts vary in shape with their state of distension. Hence they have been described in very different terms by different authors. The two oviducts pass ventrally to the terminal nerve structures, to form a common vagina, which opens between the sterna of the eighth and ninth abdominal somites. p. Colleterial glands of the left side.
The tubules of each side join a single stem, and the two ducts thus formed open by a single orifice into the vagina within the angle bounded by the nerves of the last abdominal ganglion. The two glands (right and left) have, according to Kadyi, an identical structure, and consist of tubes dividing dichotomously. But the left gland is large and hides the right, and its secretion contains crystals of Calcium oxalate. The secretion itself is a yellow granular fluid which hardens on exposure to air and forms the cocoon. This cocoon lodges as a rule sixteen eggs disposed in two rows, an egg on one side alternating with an egg on the other. The spermatheca opens in front of the colleterial duct. It consists of two short tortuous caeca with a short common duct. Spermatozoa are said by von Siebold to be found in both these caeca. The usual structure in Insecta of this apparatus is a bursa copulatrix with muscular walls and chitinous lining and an appended gland. In thus possessing two receptacula seminis instead of one, as also in having eight ovarial tubules instead of twelve, as is usually the case in Orthoptera, the Cockroach presents more or less aberrant arrangements.
Ovarial tubes. Brandt, Memoires de l'Acad. Imp. St. Petersburg, (7), xxi. 1874. Id. Das Ei, Leipzig, 1878; Id. Z. A. viii. 1885. Ovum of Nepa and Notonecta, Will, Z. W. Z. xli. 1885; of Colymbetes fuscus, Id. ibid. xliii. 1886; Of various Insecta, Korschelt, Z. A. viii. 1885; Von Wielowiejski, Z. A. ix. 1886. Micropyle and chorion, Korschelt, Z. A. vii. 1884.
Development of ovarial tubes in Insecta. Jaworoski, Z. A. v. 1882. Cf. Bal-biani, Recueil Zool. Suisse, ii. 1885; Schneider, Zool. Beitrage, i. 1885.
Genital apertures in Insecta. Palmen, Ueber paarige Ausfuhrungsgange der Geschlechtsorgane bei Insecten, Helsingfors and Leipzig, 1884; cf. Id. M. J. ix. 1883.
Development of sex ducts. Nusbaum, Z. A. v. 1882.
Spermatheca. Von Siebold, Muller's Archiv (Arch. fur Anat. und Phys.) 1837, p. 393; of P. orientalis, p. 408. Leydig, Nova Acta, xxxiii. 1867.
Colleterial glands, and egg-capsule. Kadyi, Z. A. ii. 1879. Egg-Capsule. Hallez, A. N. H. (5), xvi. 1885.
Female genital armature. De Lacaze-Duthiers, A. Sc. N. (3), xvii. 1852. Cf. Huxley, Anatomy of Invertebrata, p. 405, p. 433. Development of these parts in Insecta. Packard, Guide to the study of Insects, 1872, p. 15. In various Hymenoptera, Kraepelin, Z. W. Z. xxvii. 1873; Dewitz, ibid. xxv. 1875; xxxviii. 1877.