772 The Amerkan Naturalist. [September, 
lower lip. The convoluted intestines are loaded with fine sand 
and vegetable debris. The cartilaginous structures of the head 
have undergone astonishing development since the 5th. 
By April 20 the length has become 10 mm. There is a bud 
of tissue on each side at the base of the tail, the rudiment of the 
, future hinder limbs. The mouth is nearly surrounded by a row 
of fleshy papillae, inside of which are the rows of horny labial 
teeth. There are now two rows on each lip, the one next the 
upper beak being interrupted in the middle line. All these teeth 
are finely notched at their tops, the whole forming a most 
admirable apparatus for scraping off the layer of algae that 
covers everything in the water. Ciliary action is still going on 
over the body. 
A week later the length has increased a little. By means of 
their sucker-like mouths they adhere to the vessel in which they 
are kept. They are probably at the same time busy feeding. 
The lower lip is now provided with three rows of denticles, a 
third short row having made its appearance outside of the others. 
The eyes are more lateral than are the Rana virescens larvae. - 
Measurement of the tadpoles on the 4th of May shows their 
length to be 19 mm. The hinder limbs show signs of segmenta- 
tion. The body is jet black, with dots of gold; the belly is 
nearly covered with gilt of a brassy reflection. In one specimen 
currents of water were seen to enter the nostrils, and feebler 
currents the mouth. One was seen to come to the surface for 
air, and others to emit bubbles of air beneath the water. Obser- 
vation of these larvai and those of Acris gryllus shows that the 
water used in breathing is drawn in through the nostrils and 
emitted through the pore on the left side until about the time 
when the forelegs are to appear. It is then drawn in, principally, 
at least, by the mouth. I have also observed in the case of both 
species that after the forelegs have been set free and the tail begins 
to be observed at least a portion of the water taken in by the mouth 
is sent out by the nostrils. This may be due to the partial 
closing up of the excurrent branchial pore. The stream may 
bathe the yet present gilK; but if the water continues thus to be 
drawn in and expelled after the gills are absorbed, as I have 
