No. 405.] DEVELOPMENT AMONG ANURA. 691 
never develop to the same extent. No adhesive gland is 
formed. When the external gills are developed the tail has 
grown to a large size and has so ample a blood supply from the 
dorsal aorta and cutaneous veins that it is supposed to be an 
important organ of respiration. After hatching, the tip of the 
tail often vibrates rapidly, perhaps to insure the flow of a con- 
stant stream of water over the tail. 
Before hatching, the operculum grows back from the hyoid 
arch, and has a median spiraculum; the external gills are 
rapidly absorbed, and internal gills are developed. The stomo- 
deum breaks through, at the last stage in the egg, and the 
tadpole hatches as a free-swimming, transparent larva, with 
prominent eyes, and with no longer any trace of yolk. The 
lungs are present. On the day after hatching, pigment appears 
in the larva. 
Five weeks later the hind legs begin to develop, and the 
tail is absorbed very rapidly, until only a little of it remains. 
After the legs are formed the frog leaves the water, and the 
final absorption of the tail takes place on land. 
. The eggs of Hyla nebulosa, found in Rio de Janeiro, hatch in 
a frothy mass in the sheath of withered banana leaves, but not 
near a pool. Unlike the tadpoles of Chiromantis, which probably 
reach the water in the natural course of events, the tadpoles of 
Hyla nebulosa invariably die if they are transferred to water. 
The tadpoles of Cystignathus (Paludicola) gracilis in Brazil, 
and of a frog believed to be Rhacophorus eques in Ceylon, are 
Said to undergo part, at least, of their development out of 
Water. The eggs have been found in frothy masses on land, 
those of Cystignathus usually in the grass.in the neighbor- 
hood of pools. The adult Cystignathus, and on one occasion 
two young, were found under decaying trunks of trees, near 
dried ponds ; the larger of the two young possessed the vestige 
of a tail. The naturalist d’Orbigny found the same species in 
the Argentine Republic, where it occurs under pieces of wood, 
near the borders of lakes that are common in the sandy soil. 
The tadpoles of Rhacophorus were observed superficially and are 
Said to resemble those of the ordinary frog. 
1 For further details, see Budgett (99). 
