The alligator and its allies

by A. M. Reese

The Copulatory Organs.

The penis, [Fig. 56], usually lies completely hidden in the cloaca; with its glans projecting backwards it is strongly arched; along the convex side of the arch, which is directed towards the upper wall of the cloaca, runs a groove, which serves as a penial urethra to conduct the semen.

According to Rathke there may be recognized in connection with the penis two fibrous strands (resembling the corpora cavernosa of mammals), a corpus cavernosus urethrea, and a covering derived from the mucous membrane of the cloaca. The two fibrous strands arise from the pubis as two thick plates that soon completely fuse together by their adjacent sides to form the shaft, c, of the penis. These fused strands taper gradually towards the glans, in which they end in a point. From their mode of fusion there is left between them, on the side towards the upper wall of the cloaca, a fairly deep furrow that extends to the tip. According to Rathke these shafts are not of cavernous tissue, but the tube is lined by a layer of this tissue.

Fig. 55. Male Urogenital Apparatus of Alligator Lucius. (After Bronn.)

a, kidney; b, testis; c, vas deferens; d, ureter; e, opening of the ureter into the cloaca; f, opening of the vas deferens into the cloaca; g, upper region of the cloaca; h, hinder region of the cloaca; i, rectum.

Fig. 56. Male Organ of Alligator Lucius, XI. (From Bronn, after Rathke.)

a, the right crus penis; b, the mucous membrane of the cloaca that covers the organ; c, shaft of the penis; d, base of glans; e, point of glans; f, part of the ring muscle of the cloaca.

The glans, e, consists of two parts between which, where they leave the shaft of the penis, is a funnel-shaped hole, wider towards the free end of the penis and divided into similar lateral halves by a fold of skin. The glans is much shorter than the shaft of the penis. The covering of the penis is much thinner than the mucous membrane of the cloaca and is thinnest along the groove; it extends from the shaft over the glans without forming a foreskin.