Fig. 465.—A, diagram of male sexual organs of Carabus. B, of Blaps. C, of Hydrophilus. The heavy black lines represent the ectodermal organs; t, testis; a. g., accessory glands.—After Escherich.
The male organs are, then, the following:—
1. Two testes (Figs. 465–469, t, H, ho).
2. The two seminal ducts (vasa deferentia, v, sl, SL), whose lower or outer (distal) division becomes enlarged and acts as a seminal vesicle (vesicula seminalis; Figs. 467–469, bl, SB).
3. The common ejaculatory duct (ductus ejaculatorius), with the penis (Figs. 467–469, ag, uSG).
4. Accessory glands at the base of the vasa deferentia (glandulæ mucosæ, Figs. 465–469, a. g., dr, D), whose secretion mixes with the semen or serves for the formation of the seminal packets (sematophores).
In his paper on the internal male organs of beetles, Escherich states that those of the Carabidæ illustrate the simplest, most primitive condition (Fig. 465). A simple blind tube on each side produces spermatozoa, stores the elements, and secretes mucus. Each of these tubes opens into a somewhat larger duct, and the two unite in a common ejaculatory canal. The terminal portion in these beetles is lined with chitin, and is therefore ectodermal, and not the result of the union of the mesodermic vasa deferentia. The region corresponding to the testes, vasa deferentia, and seminal vesicles are mesodermic. Blaps (Fig. 465, B) is intermediate between the Carabidæ and Hydrophilus (Fig. 465, C). The accessory glands (a. g.) are developed, and the seminal vesicles are situated in the middle, and not at the lower end of the vasa deferentia, as in Hydrophilus.
The testes.—Each testis is composed of follicles or corresponding parts, which according to the group of insects in which they occur are united in different ways; or each testis consists of a single hank or skein-like blind tube which is enveloped by a membrane, as in the Carabidæ, Dyticidæ, or Lucanidæ.
