442 1)B. J. ANDEESO]S^ ON THE CLO.VCAIi BLADDERS 



emydagrandis, Emys Samiltonii, and Trionyx ocellatus such a com- 

 munication does exist. In this respect these animals conform 

 to the course of these canals in the crocodile. Now Geoemyda 

 grandis and Trionyx ocellattis belong to two widely separated 

 groups of Chelonia ; and the fact that the peritoneal canals 

 open into the cloaca in both would lead us to anticipate that this 

 arrangement was common to all the Chelonia which resembled 

 them in habits of life and general structure. But a more ex- 

 tended series of experiments will be necessary to establish this 

 point ; and all I insist on is, that in the males, as in the females, 

 experimented upon these canals do open into the cloaca, and in 

 this respect conform to the general type of structure distinctive 

 of the peritoneal canals of Crocodilia, and of the so-called abdo- 

 minal pores of the Cyclostomous and Ganoid fishes. 



But the view of the structure of these canals to which I wish to 

 direct more particular attention is, that in the foregoing experi- 

 ments no trace of an)"" communication between the peritoneal canals 

 and the corpora cavernosa could be observed. I was at first very 

 sceptical regarding the results I had obtained, after the very em- 

 phatic statement of Is. Greoffroy St.-Hilaire, that in his experiments 

 on Emys trijuga the mercury injected flowed freely between the pe- 

 ritoneal canal and the corpora cavernosa and vice versd,a.nA from the 

 glans into the peritoneal canal ; but as my experiments were con- 

 ducted with great care, I have thought it well to record them, be- 

 cause there are great difficulties in accepting Is. Greoftroy St.- 

 Hilaire' s explanation of the relations which, be states, subsist be- 

 tween the peritoneal canals and the corpora cavernosa. In claiming 

 for the peritoneal canals the existence of a series of minute sieve- 

 like orifices intervening between them and the corpora cavernosa, 

 he would thus establish a direct communication between the blood- 

 vascular system and the peritoneal cavity — a condition of things 

 which would be unique in the animal kingdom. Moreover, as 

 he adduces the passage of the mercury as a proof of the exist- 

 ence of these orifices between the large blood-conduit, the corpus 

 cavernosum and the peritoneal canal, we are led to suppose that 

 the blood would follow a similar course, wliich means that it passes 

 backwards and forwards over the serous or peritoneal lining of the 

 canal and the structurally different inner wall of the corpus caver- 

 nosum. Such a view of the relation of these two canals is opposed 

 to the first principles of physiology. Is. Greoffroy St.-Hilaire was 

 quite aware of these practical difficulties to the acceptance of the 



