FROGS AND TOADS. 
277 
eating spectacle. The blood, forced from the heart in 
regular pulsations, is seen to diverge into each of the main 
gill-stems, sending off lateral streams to every tiny branch- 
lot ; the red globules are seen to chase each other along 
the tortuous vessels, to pass to the extremity of every 
ramification, and then, turning, follow a backward course, 
until they roach the heart, the fountain from whence they 
issued. 
But now these organs begin to disappear : they gradu- 
ally diminish, until at length they can no longer be dis- 
cerned externally, though their function is carried on in a 
cavity of the body on each side. The little animal increases 
rapidly in size, but does not change this its fish-like form 
for a considerable period, though minor modifications may 
be traced. Thus the mouth becomes developed, the eyes 
are perfectly formed, and the tail-fin grows greatly in 
perpendicular breadth, and is a powerful organ of locomo- 
tion. The little Tadpole begins greedily to devour vege- 
table matter, and manifests the effect of this diet in the 
change of its own hue from a dull black to a soft olive- 
green, with golden specks on the under parts. 
At length the period approaches when the Tadpole must 
leave its aquatic life, and become terrestrial at least it 
must cease to respire water, and must derive its vitality 
from the air. The first step to such a change, is the de- 
velopment of limbs. First appear the hind-legs, in the 
form of a pair of minute budding warts, which lengthen, 
become bent, and shoot forth tiny toes at the extremity. 
The fore-legs, always a little later than the hind, accom- 
pany the latter in their gradual progress. As the new 
organs of motion are acquired, the old one — the vibrating 
