a4 New Species of Batracian Kepiiies. 
curious details concerning their organization, development, 
and functions. The science of experimental physiology has 
been more indebted to this than to any other class of animals. 
Frogs, being easily procured, and submitting tu torture with- 
out any expression of pain, either by cries or convulsions, 
have always been preferred by physiologists as objects of 
experiment, when the peculiarity of their organization offered 
no barriers to their views. For this purpose their remark- 
able tenacity of life offered further facilities. The heart and 
entrails may be torn out of the body, without the animal ap- 
pearing to suffer to a great degree, and produces death only 
at the end of some hours. The heart indeed affords signs of 
sensibility for many days after the appearance of life has 
ceased in other parts. The millions of these animals which 
have perished beneath the recipient of the air-pump, the ex- 
citations of the electrical machine, or of the scalpel of the 
anatomist, have given rise to the most important facts in phy- 
siology, anatomy, and natural philosophy. In every stage of 
their existence, the frogs are exposed to become the prey of 
many enemies: some quadrupeds, birds, serpents, and fish, 
live habitually upon them. In order to support this immense 
destruction, they live to a considerable age, when they escape 
their enemies, and each female discharges from six to twelve 
hundred eggs annually. 
Nothwithstanding the talent which has been employed, and 
the length of time which has elapsed, since these reptiles have 
occupied the attention of the learned of several nations, there 
exist at the present day some points of their organization in- 
volved in obscurity, and some errors have been perpetuated 
from author to author. 
In order to become better acquainted with their habits, and 
watch the progress of their developement, I have this season 
confined great numbers, of both tadpoles and frogs, in con- 
venient receptacles. 
My observations on the former were interrupted by an ac- 
cident, after an attention of rather more than two months. | 
have however collected a few facts worthy of publication. 
My specimens were of different species and of various ages ; 
but observation was more particularly directed to the larve 
or tadpole of the Rana pipiens, Linn. as being larger than any 
others inhabiting this state. 
Though not full grown, about the latter end of May they 
generally measured in total length four inches five tenths: 
