BATRACHtAm 
177 
producing a greater volume of sound swell out on each side 
of the head of the males. Among the few viviparous Ba- 
trachians known is an Alpine European salamander 
{S, atra) which brings forth its young alive. 
Unlike young fishes, the yolk is entirely absorbed before 
Fig. ^aH^.—Axolotl, or larval Salamander, showing the gills, heart (H), aortic 
branches and lungs {PA). P. pulmonary arteries; pp, pulmonary veins; A, 
bulbus arteriosus, from which the vascular arches (B) originate; 66, bran- 
chial vein; the lower A, vena cava; F, descending aorta. 
the tadpole leaves the egg. In warm climates the tadpoles 
hatch in four or five days after the eggs are laid. When 
hatched the tadpole is not so well developed as in most 
young fishes. The digestive canal at first is simple and 
straight. Afterwards it becomes remarkably long, and 
