708 THE AMERICAN NATURALIST. . [Vor. XXXIV. 
surrounded by a mucilaginous covering. They are at first very 
slightly pigmented. Tadpoles in the Zoólogical Gardens in 
London hatched in about two days; the head of the newly 
hatched tadpole is broad and flat ; the fin is developed on the tail 
to the posterior end, and there is no chimzroid lash as Parker 
(77), and subsequently the text-books, have figured; the intes- 
tine is coiled as usual. Thetadpoles in confinement had access 
to vegetable food, but subsisted entirely on an animal diet. A 
single ventral adhesive gland persists for a long time and at an 
early period occupies the whole ventral surface of the head. 
The buccal cavity is open to the exterior the day after hatch- 
ing. No jaws or beak develop. A few days after hatching a 
pair of tentacles develop on either side at the angles of the 
jaw; one of them may become bifurcated and each is provided 
with two channels through which the blood streams. External 
gills are not wholly wanting (as was formerly thought), for two 
days after hatching, when the operculum is commencing as à 
free fold, there are vascular lamelle on the first three bran- 
chial arches. The gill-slits open later than the mouth; the 
hyoid cleft opens last by a tube into the first branchial cleft, a 
long way from its opening to the exterior. At the same time 
that the gill-slits open, a tufted filtering apparatus is developed 
from the branchial arches; this becomes vascular and must, It 
is thought, be respiratory, as no internal gills develop. Hee 
opercular folds do not cover the arms, but open by a slit on 
each side, anterior to the arm. The spiracule persist for a 
long time. The pronephros develops as in the ordinary frog. 
The vascular system develops as described by Maurer for 
Rama esculenta. à 
It is evident from the foregoing review that many points Mn 
the embryology of the Anura remain to be investigated; 1t 18 
not, however, surprising that the work has been left undone, 
when we consider the geographical, the climatic, and other 
difficulties attendant upon making observations and collecting 
material. 
GERMANTOWN, PENN., 1900. 
