No. 405.] DEVELOPMENT AMONG ANURA. 695 
said that the whole yolk-mass was invested with a “tunic” 
and converted into a spiral intestine, returning to the trunk 
through the middle of the coil! The nostrils in this stage 
were seen as round terminal depressions. 
In the last stage toes were formed; the skin was furnished 
with papilla and protuberances ; the intestine had increased 
in length and was still coiled; the mouth, as in the preceding 
stages, was placed under the head, at a little distance from the 
anterior end. Another account states that the horny jaws are 
not developed. The tail in all embryonic stages was provided 
with the usual muscles as if for swimming, and was folded 
against the side of the egg. Wyman shows that, after the 
supply of gelatinous substance around the egg has been ex- 
hausted, the tadpole still continues to increase in size, and he 
concludes that it must therefore grow at the expense of mate- 
rial from the mother, probably by a secretion of the wall of 
the cell. In summing up the development of Pipa, Wyman 
notes that the embryo goes through the usual metamorphosis, 
having internal and external gills and lungs, also a tail adapted 
to swimming, although the gills and tail are never used as in 
the frog. The external branchiz are lost at a very early 
period, and the tail is absorbed before the animal escapes 
from the back of the parent. 
The folds of skin covering the internal gills differ from the 
operculum of the frog in that they open on both sides, and 
the anterior legs are not covered by them. These relations 
are similar to those in the larva of Dactylethra, the other 
representative of the primitive suborder of Aglossa. The 
Presence of external gills has been doubted at various times, 
but the balance of evidence and the last word on the subject 
scem to show that they exist for a short period. 
An early writer, according to subsequent quotations, affirmed 
that the tail is devoid of pigment, and believed that it is an 
embryonic breathing organ. This idea was entertained at a 
time when the presence of gills was not known; it is not 
in accordance with Wyman’s account, nor with Spallanzani's 
(1785), who concluded, after a careful examination, that the tail 
does not differ from that of the ordinary tadpole. Furthermore, 
