AND PERITONEAL CANALS IN CHELONIA. 443 



view which he had propounded regarding the relations of these 

 structures, and he remarks that he had never observed blood in 

 the peritoneal canal ; but to account for this, he conjectured that 

 the supposed minute orifices leading into the corpora cavernosa 

 were related to the cavity of that tube much in the same way that 

 the openings of the seminal tubes are to the urethral canal of the 

 higher vertebrates, the orifices of which are so protected that the 

 urine in its passage outwards is eflaciently denied access to them, 

 This comparison leads to the supposition that their orifices exist 

 only for the transmission of fluid from the peritoneal canal to the 

 corpora cavernosa, which would remove one aspect of the diffi- 

 culty. But as there is no analogy between the closed spongy sub- 

 stance of the glans which is directly continuous with the corpora 

 cavernosa into which the blood-vessels pour the fluid, and the ex- 

 creting tract of the urethra, the theory implied in the comparison 

 instituted by Is. Geoffroy St.-Hilaire, that a fluid passes from the 

 peritoneal canals into the corpora cavernosa, is a practical diffi- 

 culty of the greatest moment. What is the fluid which would so 

 pass ? If, as he allows, there exists in the female tortoise a 

 direct communication between the peritoneal canals and the 

 cloaca, and, as I have proved, in the male Geoemyda grandis and 

 T. ocellatus, as these orifices are not valvular, the likelihood 

 is, that as the cloaca is distended with water this fluid finds 

 its way into those canals, it may be even into the peritoneal 

 cavity ; and we should thus have to accept the conclusion that 

 the fluid they transmit to the corpora cavernosa, and thus to 

 the blood, was partly composed of the secretion of the peritoneal 

 cavity diluted witli water. 



It is unnecessary to say any more regarding these views, my 

 purpose not being controversy, but merely to direct more attention 

 to the structures which have, doubtless, an important bearing on 

 the economy of these remarkable animals. My own opinion is that 

 they are in no vray related to the generative functions, but that 

 they are, as has been suggested by Dume'ril and Bibron *, probably 

 accessory and subordinate to transpiration, admitting water into 

 the peritoneal cavity, which adapts the animal to the change to 

 which it is subjected when exposed to the air in too high or too 

 dry a temperature. 



Little or nothing is known regarding the development of these 

 canals in the Chelonia ; but as they have associated with them 

 in the adult condition a pair of generative tubes and well-defined 

 * Erp6t. Gen. vol. . p. 195. 



