. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. GENERATIVE ORGANS. 541 lid. fluence of the secretion of an accessory gland. Beneath the recepta- culum seminis, a large pouch-like diverticulum, the bursa copulatrix, which assumes the function of the vagina, is sometimes separated from the vagina. In the butterflies (fig. 448) a narrow duct serves to convey the sperm from this bursa, which opens separately, to the receptaculum. The male generative organs consist of paired testes and their vasa deferentia, of a common ductus ejaculatorius a
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. GENERATIVE ORGANS. 541 lid. fluence of the secretion of an accessory gland. Beneath the recepta- culum seminis, a large pouch-like diverticulum, the bursa copulatrix, which assumes the function of the vagina, is sometimes separated from the vagina. In the butterflies (fig. 448) a narrow duct serves to convey the sperm from this bursa, which opens separately, to the receptaculum. The male generative organs consist of paired testes and their vasa deferentia, of a common ductus ejaculatorius and of the external copulatory organ (fig. 450). The testes are long blind tubes, which are present either singly or in number on either side, and are often coiled together so as to form a seemingly compact brightly-coloured body. They may also be united to form an unpaired organ in the middle line. The testicular tubes are prolonged on either side into a usually coiled efferent duct or vas deferens, the lower end of which dilates considerably, and may even swell out to the form of a vesicle (vesicula seminalis). At the point where the two vasa deferentia join to form the muscular ductus ejaculatorius, one or more glandular tubes often pour their coagulable secretion into the latter; the secretion serving to form a case round the balls of spermatozoa. The transference of the sperrnato- phores into the body of the female is effected by a horny tube or groove which surrounds the end of the ductus ejaculatorius. This tube, when not in use, usually lies retracted in the abdomen, and when protruded is surrounded by external organs for attachment (valves or pincers), as by a sheath. In exceptional cases (Libellula) the copulatory apparatus which serves to transfer the sperm is remote from the generative opening, as in the male spiders, being placed on the ventral side of the enlarged second abdominal segment. Almost all insects are oviparous, and only a few, as the Tachincv, FIG. 449.
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