The Common Bullfrog 



stantly opened and shut in breathing, the rudimentary tongue 

 is visible on its floor. The fringe of the lower lip is still present, 

 but the horny beak within seems to have disappeared. From 

 this time to the end of the change the tadpole does not eat. 



The elbow of the left arm is now visible within the breathing- 

 pore. (Fig. 284.) The skin of the right side has become thinner, 

 so that the movement of the right arm is plainly visible, and 

 before night the movement has worn a hole through the skin, and 

 the right elbow is plainly visible also. We are not surprised in 

 the morning to see the left arm projecting through the breathing- 

 pore. Two hours later the right arm is pushed out so that both 

 arms are now free. (Fig. 285.) These arms begin their growth 

 at the time when the back legs appear, but are concealed within 

 the gill-chambers. (See Fig. 280.) 



On this day the tadpole breathes with much effort. The 

 mouth, which is still increasing in width and shows the develop- 

 ing tongue within, is opened and shut constantly. The gills have 

 begun to be absorbed, and the lungs, although developed, are not 

 yet fully in use. The left arm blocks up the breathing-pore, so that 

 little of the water sent to the gills can escape there. (Fig. 286.) 

 The water is taken in at the mouth and nostrils to the gills of 

 the throat, and is expelled through the mouth, instead of through 

 the breathing-pore. The lungs are used somewhat; the tadpole 

 very often comes to the surface of the water and gives out a 

 bubble of air from the mouth. In a very few days (by July Qth) 

 a decided change takes place: the gills are wholly absorbed; the 

 lungs are fully in use; the mouth is kept closed, and the tadpole 

 is an air-breather. Now the tadpole spends much time at the 

 surface of the water, sometimes rushing madly from the bottom 

 to exchange a bubble of impure air for fresh. (Fig. 288.) He 

 is very comfortable out of water. (Fig. 287.) 



The developing tadpole is white on the under side of the 

 body and yellow on the under side of the legs. The mouth is 

 open back to a point on a line with the front of the eye. The 

 legs are greatly developed, and the tail is becoming shorter and 

 narrower. It is dark in color and almost black at its end. The 

 tail is no longer used in swimming, but the legs do all of the work. 

 (Fig. 288.) The process of absorption has begun by which all 

 the living part of the tail retreats into the body of the tadpole 

 and helps in the formation of new organs. The wandering white- 



237 



