2 92 PICK EL. [Vol. II. 



by blowing air into the living animal through the cloaca he 

 could enlarge these vessels so much that they compelled the 

 animal to project its extremities from its carapace and spread 

 them out. The wall of the bladders is, according to Duvernoy 

 (7), very thin, and is composed of two layers — - an outer peri- 

 toneal layer, which is very rich in blood vessels, and an inner 

 mucous membrane. He did not detect muscle fibers. He 

 ascribes to these bladders a most peculiar function: "the ani- 

 mal can fill them with water, perhaps also with air, and can 

 make use of them in diminishing its specific gravity. Hence 

 we can explain why they are not found in land tortoises, which 

 are not aquatic animals, and why they are absent even in the sea 

 turtles, since the bodies of the animals are broad and flattened, 

 and their extremities transformed into pinnate feet, and since, 

 moreover, the specific gravity of sea water is greater than 

 that of fresh water, they can dispense with the means of 

 floating." 



It is even comprehensible, as Duvernoy (7) shows, that they 

 should be absent in TrionycJiidac. In these turtles the extrem- 

 ities form strong rudders, as in the Emydidae, and their bodies 

 are broad and flattened, thus enabling them to swim and float with 

 ease. Lesueur (10) states that in Cistiido carolijia ( TcjTapenc Car- 

 olina Linne, according to Strauch) these bladders are very small, 

 and Duvernoy (7) concludes from this statement that their man- 

 ner of living is the mean between that of the land turtles and 

 the Emydidae. Stannius (16) merely says of these bladders, 

 that, at least in the families Testitiidinidac and Ejnydidae, a pair 

 of sacs open into the cloaca. Owen (13), who calls them 

 " cloacal sacculi," considers them to be only transitory struc- 

 tures. Budge (5) critically examined them in Cistudo amboinen- 

 sis Gray (Tcrrapene amboincnsis Daudin, according to Strauch) 

 {Cyclemis amboincnsis Boulenger), and found them in both 

 sexes. He calls them "anal bladders." They consist of two 

 membranes ; the peritoneum appears to make up only the outer 

 surface of the organ; and next to the posterior part of the blad- 

 der wall he finds an oblique striated muscle, which proceeds 

 from the carapace and extends nearly up to the muscular 

 cloaca. Here it becomes sinewy and forms a ligament, which 



