er such circumstances the adhesion may
prevent separation. Also, it may serve to prevent displacement of a
clasping male by a rival. Anderson (_op. cit._) who observed many
details of the mating behavior of _G. carolinensis_, both in the
laboratory and under natural conditions, mentioned no such adhesion
between members of a pair.

Anderson (_op. cit._: 31) discussed the possibility that reproductive
isolation might arise in sympatric populations, such as those of _G.
carolinensis_ in southern Louisiana, through inherent differences in
time of spawning. However, in _G. olivacea_ at least, such isolation
would be prevented by individual males returning to breed at different
times in the same season. Furthermore, individual differences in choice
of breeding time probably result from environmental factors rather than
genetic factors in most instances. In _G. olivacea_ in Kansas, time of
breeding is controlled by the distribution of heavy rainfall creating
favorable conditions. Onset of the breeding season may be hastened or
delayed, or an entire year may be missed because of summer drought. If
favorable heavy rains are well distributed throughout the summer, frogs
of age classes that are not yet sexually mature in the early part of
the breeding season, may comprise the bulk of the breeding population in
late summer.

DEVELOPMENT OF EGGS AND LARVAE

Eggs laid on June 5 by the pair kept in the laboratory were hatching on
June 7, on the average approximately 48 hours from the time of laying.
By June 8 all the eggs had hatched and the tadpoles were active. On
August 28 and 29 thousands of newly metamorphosed young were in evidence
on wet soil at the pond margin; in some the head still was tadpolelike
and they had a vestige of the tail stump. These young were remarkably
uniform in size, 15 to 16 mm. (the smallest one found was 14-1/2 mm.)
and almost all of them had originated from eggs laid after heavy
precipitation, totalling 3.22 inches, in the first 36 hours of August.
Allowing one day for adults to reach the pond and spawn, and two days
more for eggs to hatch, the tadpole stage must have lasted approximately
24 days in this crop of young.

Wright and Wright (1949: 582) stated that the tadpoles metamorphosed
after 30 to 50 days, and that the newly metamorphosed frogs are 10 to 12
mm. in length. Length of time required for larval development probably
varies a great deal depending on the interaction of several factors su