(2021). In the Chelonian Reptiles the penis is much more perfectly developed, and really constitutes a very efficient intromittent instrument. The two corpora cavernosa, after commencing separately, approach each other, and become united along the mesial line so as to form a single organ of considerable size, terminated at its extremity by a glans-like dilatation. There is, however, no corpus spongiosum, nor urethral canal, properly so called: the latter is represented by a deep groove, which runs along the upper surface of the penis from the cloaca to the extremity of the organ; and it is along this groove that the spermatic fluid is conveyed during coitus.

(2022). On making a section of this strange apparatus, two canals are discovered, running one on each side of the central furrow, along the whole length of the organ as far as the glans, where they terminate without at all communicating with the exterior; but on tracing them in the opposite direction, they are found to be derived from the peritoneal cavity, into which they open by distinct orifices 1.

* Vide Rusconi, Observations anatomiques sur la Sirene, mise en parallele avec le Protee et le Tetard do la Salamandre aquatique. Pavie, 1837. 1 Cuvier, Anat. Comp. torn. v. p. 115.

(2023). Two retractor muscles, derived from the pelvis, and extending along the under surface of the penis quite to its extremity, fold the whole organ back into the cloaca, where it lies concealed when not in use.

(2024). In the Crocodiles and higher Saurians the penis in its structure resembles that of the Tortoise; and instead of a urethra, there is merely a deep groove traversing the upper surface of the organ, along which the semen trickles out of the cloaca.

(2025). Throughout all the Reptile families the organization of the female generative system is so extremely similar, that one example will be abundantly sufficient for our purpose, the same description, in fact, being equally applicable to the Saurian, the Chelonian, and the Ophidian orders. The ovaries occupy their ordinary position in the lumbar region of the abdomen, where they are attached on each side of the vertebral column by a broad fold of peritoneum: their structure is in all essential points precisely similar to those of the Amphibia; but, owing to the increased proportionate size of the individual ova formed by their vascular membrane, they resemble a string of beads, or assume somewhat of a racemose appearance. The oviducts are long and flex-uous; they commence by a wide orifice (fig. 353, 6 m), by which the germs are taken up from the ruptured ovisacs of the ovaria in the same way as those of Mammalia are seized by the fimbriated extremities of the Fallopian tubes. The first portion of the oviduct is thin and intestiniform; but lower down, where the investments of the egg are formed, its walls become thicker, and assume a glandular character (n, o, p); they finally open into the cloaca; and the mode of their termination in the Tortoise is exhibited in the accompanying figure, where m, m, e m indicate the terminal portion of the right oviduct laid open, the left (a m, b m) being shown through its entire length.

(2026). The formation of the egg and the development of the embryo are similar in all the oviparous Vertebrata; it will therefore be more convenient, and prevent unnecessary repetition, if we defer the consideration of this important subject to the next chapter, - the reader bearing in mind that in all essential particulars the details which will be given there, when we come to consider the growth of the Bird in ovo, . are equally applicable to the Chelonian, Ophidian, and Saurian Reptiles.

Oviduct and ovum of female Tortoise. (After Bojanus.)

Fig. 353. Oviduct and ovum of female Tortoise. (After Bojanus).