RErTTMA. 589 



perforate, is covered with sharp spines, and is obviously rather 

 adapted to take firm hold of the cloaca of the female than to form 

 a channel for the introduction of the seminal fluid. 



(654.) In the Chelonian Reptiles the penis is much more perfectly 

 developed, and really constitutes a very efficient intromittent in- 

 strument. 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 ex- 

 tremity by a glans-like dilatation. There is, however, no corpus 

 spongiosum, or urethral canal, properly so called : the latter is re- 

 presented 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. 



On making a section of this strange apparatus, two canals are dis- 

 covered, 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.* 



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. 



In the Crocodiles and higher Saurians the penis in its structure 

 resembles that of the Tortoise ; and, instead of an urethra, there is 

 merely a deep groove traversing the upper surface of the organ, 

 along which the semen trickles out of the cloaca. 



(655.) 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 pojnts 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 flexuous ; they commence by a wide 

 orifice {Jig. 267, b M), by which the germs are taken up from the 

 * Cuv. Anat. Comp. torn. v. p. 115. 



