436 1)R. J. ANDEESOK ON THE CLOA.CAL BLADDITfia 



onorei, Pangshura tecta, P. tentoria, P. smithii, P.Jlaviventris, P. 

 sylhetensis, Cuora amhoinensis, Cyclemys dentata, Geoemyda depressa, 

 G. grandis, and Platysternum megacepJialum. In Pangshura, 

 Cyclemys, Platysternum, and Geoemyda the inner walls of these 

 bladders are covered over vpith long villi of different forms, and 

 which in some are not confined to the bladders, but enclosed be- 

 tween them over the fold of the upper wall of the cloaca ; whereas 

 in all the true Emydes and in the Batagurs their inner walls 

 appear to be smooth. 



It is a noteworthy fact that the cloacal bladders do not occur, 

 as far as my researches go, in Testudo, Pyxidea, Trionyx, Cliitra, 

 and Peloclielys. This is a significant circumstance, which suggests 

 the reflection, that these bladders are related to the habits of life 

 of the animals possessing them, because on viewing their distri- 

 bution, as indicated by these observations, it is evident thit they 

 are confined to the forms which lead a semiterrestrial and semi- 

 aquatic life, those animals which are essentially terrestrial in their 

 habits and those which are truly aquatic being unprovided with 

 them. It would thus seem, a priori, that it is owing to their exist- 

 ence in the Emydes and Batagurs that these forms are endowed 

 with a diversity of habit above their fellows — because there is no 

 very wide line of distinction, apart from these bladders, between 

 the general anatomy of an Emyde and a terrestrial tortoise, 

 beyond perhaps that the lung of an Emyde, like that of a Trionyx, 

 is more invested with muscular si^bstance, and the disposition of 

 tlie nostrils differs somewhat. 



These bladders are capacious sacs, opening, as I have stated, on 

 each side of the cloaca, near its anterior extremity ; and they occupy 

 the groin and project into the peritoneal cavity, covered, of course, 

 by the peritoneum, and having the lung in certain species lying 

 directly in contact with a considerable extent of their upper 

 border. By the nature of the fold which intervenes between 

 their openings, the portion of the cloaca anterior to them can be 

 shut off by the apposition of the fold to the floor of the cloaca, so 

 that, for the time being, the bladders may be in direct communi- 

 cation with the cloaca, to the complete exclusion of all the other 

 openings except the external anus. These circumstances seem also 

 10 favour the supposition that these bladders are in some way 

 functionally related to the aquatic aspect of their existence, since 

 it is an acknowledged fact that some Chelouia draw in and eject 

 water from the cloaca, like the Holothuridsc axid other allied in- 



