76 
AMPHIBIA. 
INTRODUCTORY OBSERVATIONS. 
Tue doctrine of continuous affinities could scarcely 
receive a more striking illustration in the animal kingdom 
than is afforded by the interesting group constituting the 
Ampursia of modern authors. Intermediate in their struc- 
ture, and, in many forms, in their habits and mode of life 
also, between the fishes and the true reptiles, they bear a 
still more interesting relation to these classes, in that 
remarkable change which many of them undergo at a 
certain period of life, by which they become transformed 
from the nature and habits of the former, to those of the 
latter class; and thus exhibit in their own individual life a 
beautiful and complete example of transition of organiza-*% 
tion; a subject which constitutes one of the most impor- 
tant theories connected with the higher departments of 
Zoological science. To any person capable of appre- 
ciating the interest attached to the study of physiological 
phenomena, the contemplation of an animal which at one 
period of its life is endowed exclusively with the organs 
of aqudtic respiration, resembling the gills of fishes, with 
means of locomotion adapted only to a constant residence 
in the water, and with a digestive apparatus fitted exclu- 
sively for the assimilation of vegetable food, assuming by 
degrees the function of atmospheric respiration, acquirmg 
limbs which are formed for leaping on land with great 
strength and agility, and manifesting the most voracious 
