\g6 AMPHIBIA 



the back forming a horse-shoe-shaped fold on the sacral region, 

 which gradually deepens ; the inner wall of the pouch is there- 

 fore part of the outer layer of the skin turned inwards. (Plate 

 XVI., B, C.) How the eggs are introduced into the pouch is still 

 unknown. In most species of this genus, the opening to this 

 invaginated dorsal fold is small and situated on the posterior 

 part of the back, often so small, when the pouch is distended by 

 the ova, as to simulate a second anal opening. In one species, 

 however, Nototrema pygmcEum, from Venezuela, the pouch is 

 formed by two lateral folds, meeting on the middle line of the 

 back, a mere slit separating them when the back is filled with 

 eggs. 



In some species, Nototrema marsupiatum, and N. plumbeum, 

 the eggs are large and numerous (about ioo), and, as fn A/ytes, 

 only a part of the metamorphosis is undergone within them, 

 the young escaping from the pouch as ordinary tadpoles, 

 with a powerful tail, internal gills, and a beak-like mouth 

 surrounded by a large circular lip. In others, N. oviferum, N. 

 testudineum, N. fissipes, N. cornutum, and N. pygmceum, the 

 eggs are enormous and few in number (four to sixteen) and in 

 these species the whole development takes place within the 

 pouch, which the young frog leaves in the perfect condition, 

 differing only in size from its parents. Within the pouch, the 

 breathing organs of the larvae consist of a pair of bell-shaped 

 membranes, veined with a capillary network, each connected 

 with the second and third branchial arches by a pair of string- 

 like filaments. These gills, the form of which can only be seen 

 by floating them in water, form a sort of envelope to the 

 embryo, like an allantois, and may be designated by the term 

 allantoic gills, which has been proposed for the lobate gills of 

 the Tailed Batrachian Autodax. 



Amphignathodon guentheri, the sole representative of the 

 family Amphignathodontidae, which inhabits the Andes of 

 Ecuador, is provided with a dorsal pouch similar to that of 

 Nototrema marsupiatum, but the eggs are still unknown. 



(2) C. c. The female of the Ceylonese Rhacophorus reticu- 

 laris carries its eggs on the belly, which bears shallow impres- 

 sion when the eggs are removed. These, in the single specimen 

 observed, measuring forty-seven millimetres from snout to vent, 

 were spherical and unpigmented, four to five millimetres in 



