The nervous system has been examined by Giebel in _Lipeurus bacillus_; there is a supra- and an infra-oesophageal ganglion, and three thoracic, but no abdominal ganglia. The supra-oesophageal is remarkably small, in fact not larger than the infra-oesophageal; it consists evidently of two conjoined halves. The alimentary canal has a slender, elongate oesophagus, dilated behind into a crop; this is frequently received between two cornua formed by the anterior part of the stomach, which, except for these, is simply tubular in form, though somewhat narrower at the posterior extremity. In some forms—Philopterides—the crop is of a very peculiar nature (Fig. 218), forming an abrupt paunch separated from the stomach by the {348}posterior portion of the oesophagus. There are only four Malpighian tubes; in some species the basal half of each tube is much dilated. The two divisions of the intestine are short and are separated by the intervention of a glandular girdle. Salivary glands exist; Giebel figures what we may consider to be an enormous salivary reservoir as existing in _Menopon leucostomum_. The testes and ovaries are of a simple nature. The former consist of two or three capsules, each having a terminal thread; the vasa deferentia are tortuous and of variable length; they lead into the anterior part of the ejaculatory duct, where also opens the elongate duct proceeding from the bicapsular vesicula seminalis; these structures have been figured by Grosse[272] as well as by Giebel. The ovaries consist of three to five short egg-tubes on each side; the two oviducts combine to form a short common duct with which there is connected a receptaculum seminis. [Illustration: FIG. 218.—Alimentary canal of _Docophorus fuscicollis_. (After Giebel.) _a_, Oesophagus; _b_, paunch; _a′_, posterior division of oesophagus; _c_, chylific ventricle or stomach; _d_, Malpighian tubes; _e_, small intestine; _f_, glandular girdle; _g_, rectum.] The eggs of some Mallophaga have been figured by Melnikow;[273] they possess at one extremity a cover with a multiple micropyle-apparatus, and at the opposite pole are provided with seta-like appendages. They are very like the eggs of the true lice, and are said in some cases to be suspended by threads to the hairs or feathers after the fashion of the eggs of Pediculi. Little is known as to the development; the young are extremely like the adult, and are thought to moult frequently; the duration of life is quite unknown.