The number of the rectal bands (six) is worthy of remark. We find six sets of folds in the gizzard and small intestine of the Cockroach, six bundles of Malpighian tubules, with six intermediate epitheliated bands. There are also six longitudinal bands in the intestine of the Lobster and Crayfish. The tendency to produce a six-banded stomodæum and proctodæum may possibly be related to the six theoretical elements (two tergal, two pleural, two sternal,) traceable in the Arthropod exoskeleton, of which the proctodæum and stomodæum are reflected folds. The anus of the Cockroach opens beneath the tenth tergum, and between two “podical” plates. Anal glands, such as occur in some Beetles, have not been discovered in Cockroaches. _Appendages. The Salivary Glands._ The three principal appendages of the alimentary canal of the Cockroach are outgrowths of the three primary divisions of the digestive tube; the salivary glands are diverticula of the stomodæum, the cæcal tubes of the mesenteron, and the Malpighian tubules of the proctodæum. [Illustration: Fig. 71.--Salivary Glands and Receptacle, right side. The arrow marks the opening of the common duct on the back of the lingua. A, side view of lingua; B, front view of lingua.] A large salivary gland and reservoir lie on each side of the œsophagus and crop. The gland is a thin foliaceous mass about 1/3 in. long, and composed of numerous acini, which are grouped into two principal lobes. The efferent ducts form a trunk, which receives a branch from a small accessory lobe, and then unites with its fellow. The common glandular duct thus formed opens into the much larger common receptacular duct, formed by the union of paired outlets from the salivary reservoirs. The common salivary duct opens beneath the lingua. Each salivary reservoir is an oval sac with transparent walls, and about half as long again as the gland. The ducts and reservoirs have a chitinous lining, and the ducts exhibit a transverse marking like that of a tracheal tube. When examined with high powers the wall of the salivary gland shows a network of protoplasm with large scattered nuclei, resting upon a structureless chitinous membrane. The salivary glands are unusually large in most Orthoptera.[129] In other orders they are of variable occurrence and of very unequal development. [129] Except in Dragon-flies and Ephemeræ. _The Cæcal Tubes._ There are eight (sometimes fewer) cæcal tubes arranged in a ring round the fore end of the chylific stomach; they vary in length, the longer ones, which are about equal to the length of the stomach itself, usually alternating with shorter ones, though irregularities of arrangement are common. The tubes are diverticula of the stomach and lined by a similar epithelium. In the living animal they are sometimes filled with a whitish granular fluid.