246 THE LOG OF THE SUNi 



and body yrhicli are susceptible to IHe watery 

 vibrations. These points are minute cavities, sur- 

 rounded with tiny cilia or hairs, which connect 

 with the ends of the nerves. 



The ears of the frogs and all higher animals 

 are, like the tongue-bone and the lower jaw, 

 derived originally from portions of gills, which 

 the aquatic ancestors of living animals used to 

 draw the oxygen from the water. This is one of 

 the most wonderfid and interesting changes which 

 the study of evolution has unfolded to our 

 knowledge. 



The disproportionate voices are produced by 

 means of an extra amount of skin on the throat, 

 which is distensible and acts as a drum to increase 

 the volume of sound. In certain bullfrogs which 

 grow to be as large as the head of a man, the bel- 

 lowing power is deafening and is audible for miles. 

 In Chile a small species of frog, measuring only 

 about an inch in length, has two internal vocal 

 sacs which are put to a unique use. "Where these 

 frogs live, water is very scarce and the poUiwogs 

 have no chance to live and develop in pools, as is 

 ordinarily the case. So when the eggs are laid, 

 they are immediately taken by the male frog and 

 placed in these capacious sacs, which serve as 

 nurseries for them all through their hatching and 

 growing period of life. Although there is no wa- 

 ter in these chambers, yet their gills grow out and 

 are reabsorbed, just as is the case in ordinary 



