330 RANID2E.
Although so closely allied and liviug side by side in
many localities, these two species never appear to in-
terbreed. As in B. temporaria and B. arvalis, this is
probably to be ascribed mainly to the great difference
in the seminal elements, as mentioned on p. 77 of the
Introduction.
Eggs. — According to Count Peracca, to whom I
am also indebted for eggs of this frog, the vitelline
sphere is blackish-brown, with the lower third white,
and measures If mm.

the mucilaginous envelop is
also smaller than in B. agilis and B. temporaria, 6 or
Fig. 120.
7 mm. in diameter. The embryo, on leaving the egg
on the thirteenth or fourteenth day, is only half as
long as that of B. agilis.
Tadpole (PL III, fig. 6). — Intermediate between B.
temporaria and B. agilis. Width of mouth equalling
the distance between the nostrils and two-thirds the
distance between the eyes. Series of labial teeth f ,
the second upper series very widely interrupted in the
middle, the third extremely short

first lower series
very short, hardly half the length of the second;
fourth interrupted in the middle. Beak as in B. tem-
poraria. Tail acutely pointed, twice as long as the
body, its depth one-third its length. Lines of muci-
ferous crypts very distinct, as in B. agilis.
Brown above, whitish beneath

caudal crests
whitish, dotted with dark brown, the upper with
some larger