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PACIFIC SCIENCE, Vol. IV, July, 1950 
spawned in a weedy place on the ground. 
The number of eggs in one hatch was usually 
about 30. At the time of each collection it 
was noticed that a considerable number of 
eggs with large yellow yolks could be seen 
through the skin in the abdomens of large 
frogs. These observations lead to the con- 
clusion that the frogs have no definite spawn- 
ing time, but spawn every month throughout 
the year. 
Metamorphosis is completed so rapidly 
that the first stage observed was probably 
close to the earliest stage. Apparently, the 
time required to complete the metamorphosis 
is about 3 weeks. 
The characteristic features of the meta- 
morphosis of this frog are the extreme swell- 
ing of the abdominal skin and the absence 
of both external gills and gill clefts. The 
larva does not pass a free-swimming stage in 
water; therefore external gills for respiration 
are unnecessary. The larva grows rapidly 
within the egg, and metabolism takes place 
actively. The expansion of abdominal skin 
or the increase of body surface and the abun- 
dant blood vessels in the skin may be helpful 
in increasing respiration through the skin. 
In addition to these characteristics, the larva 
depends wholly upon the yolk for nutriment 
throughout metamorphosis, and its yolk is 
large, like that of a fish egg. Observations on 
the cleavage of the egg were not made. 
Hitherto only two species of frogs have 
been known to exhibit behavior more or less 
similar to that of the Palau frog: Hy lodes 
( = Eleutherodactylus ) martinicensis ( Peters 
1876; Lynn 1940) and Rana opisthodon 
(Boulenger 1886). Both of them undergo 
their whole metamorphosis within their eggs, 
and their embryos possess neither gills nor 
gill openings. 
Hylodes martinicensis lays its eggs on a 
broad leaf of a plant, and the eggs are then 
glued to the leaf. The egg measures 4-5 mm. 
in diameter. The metamorphosis is com- 
pleted during 2 1 days, approximately the 
Fig. 3. Some external features of the adult 
frog, a, Lateral view of the head ( approx. X 1-6; 
o, outer nostril; r, rostrum; s, skin fold; t, tympa- 
num ) ; b, buccal cavity of the large frog; c, same of 
the small frog (b and c, approx. X 2; i, internal 
nostril; 1, lower jaw; t, tongue; v, vomerine tooth 
plate; u, upper jaw); d, palm and fingers (approx. 
X 2.6; 1, 2, etc., the first, second, etc., fingers); 
e, metatarsus and toes (approx. X 2.6; 1, 2, etc., 
the first, second, etc., toes). 
same time as was observed for the Palau frog. 
Its most noteworthy characteristic is the de- 
velopment of a large well-vascularized tail, 
the function of which is to serve as a respira- 
tory organ, just as the extreme expansion of 
the abdominal skin of the Palau frog does 
for it. 
Rana opisthodon deposits its eggs in moist 
crevices of rock close to water. Its egg meas- 
ures 6-10 mm. in diameter. Its embryo de- 
velops without any evidence of a tail, and 
has as breathing organs several regular trans- 
verse folds on each side of the abdomen 
which function in a manner quite similar to 
Hylodes ’ tail. Thus the Palau frog is entirely 
different from these two species. 
At present it seems that the data are not 
sufficient to determine the genus to which the 
Palau frog belongs. Although both hand and 
foot well resemble those of Hylodes, the 
other general features rather resemble those 
of the Ranidae, and the frog probably is a 
new species of Rana. The two types of frogs 
