440 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1959 
of producing the foam mass. Before the eggs appear she ejects a 
small amount of fluid, and this she beats into a froth by moving her 
feet medially and laterally and turning them as she crosses them on 
the midline. When the foam for holding the eggs has been prepared, 
the eggs and the fluid come out together. During the egg-laying 
process, the male is passive, grasping the female under the armpits 
and simply holding his body closely applied to her back, his eyes half 
closed. His pelvic region is bent down with the cloacal opening near 
that of the female. Apparently the eggs are fertilized as they leave 
the cloaca of the female. When the egg-laying process has been 
completed, the female stands up on her forelimbs and the male tries 
to get away from the foam in which the distal ends of his hind legs 
are buried. The female usually gets away from the foam later by 
moving her legs and body sideways with the help of large sticky 
finger disks. The foam is white at first but in a few moments changes 
to light brown. The eggs, which are without pigmentation, are scat- 
tered singly or in small groups in the big foam mass but are mostly 
concentrated near the basal part where the foam is attached to the 
substrate. The incubation period apparently varies with the tem- 
perature, and in some cases has been known to take from 6 to 7 days. 
The tadpoles also hatch in different stages of development. Some 
of the newly hatched individuals have external gills fully exposed 
while others have their external gills partly covered by the oper- 
culum and are much more heavily pigmented. Near the time of 
hatching, the foam containing the embryos begins to liquefy and the 
active movement of the fully developed embryos or tadpoles in the 
liquefied foam drops them into the water below. Sometimes the 
whole egg foam mass with its contained tadpoles may be washed down 
by rain into the pool below. When the liquefied foam drops into the 
water the tiny bubbles in it disappear and the tadpoles swim actively 
in the water. A few rhacophorids lack the habit of “egg beating.” 
For example, African frogs of the genus Hyperolius lay their eggs 
in small clusters directly in the water. Hassina is apparently quite 
closely related to Hyperolius, and it likewise lacks the habit of “egg 
beating.” Its eggs are small and pigmented and laid singly or in 
pairs in the water. 
Microhylidae.—In. the narrow-mouthed toad, Microhyla carolinen- 
sis, the eggs are pigmented, firm, and rather distinctively shaped. 
The complement ranges from 700 to 1,000 eggs which float at the 
surface film. The tiny tadpoles lack teeth on the mandibles. They 
metamorphose, in a period ranging from as little as 20 to as much 
as 70 days, into tiny frogs. This sort of life history is fairly typical 
of most microhylids but not of all of them. Some species lack the 
prolonged free-swimming tadpole stage; either the egg hatches as 
an advanced-staged tadpole or metamorphosis is completed within 
