102 CHAPTERS ON THE NATURAL HISTORY 



num. and many other mammals, raptorial birds, and snakes and 

 other reptiles. Some fishes also prey upon them. 



In the June number of Appleton's Popular Science Monthly 

 (1896) I contributed an article, entitled " Frogs and their Uses," 

 it being illustrated by a reproduction of a photograph of our 

 Bullfrog (Rana catesbiana) (p. 181), and this figure is given here 

 as one well showing the external form of this species. 



Mivart claims a frog to be "' a tailless, lung-breathing, branch- 

 iate vertebrate, with, four limbs typically differentiated, under- 

 going a complete metamorphosis, and provided with teeth along 

 the margins of the upper jaw." This last character is one that 

 distinguishes the frogs from the toads, while from other batrach- 

 ians the frogs are at once separated by the absence of a tail. 

 Both frogs and toads hibernate in the winter, coming forth in the 

 spring. The process of development in toads is very similar to 

 that of the frogs, only the eggs are strung out in links instead of 

 being in a mass. These long chains of eggs are drawn out of the 

 body of the female by the hind legs of the male, while she is in 

 the water. 



In this country we also have in the Northern and Eastern 

 States one of the best known of all those little arboreal batrach- 

 ians, vernacularly known as tree-toads, or more properly tree- 

 frogs, though I will call them " toads " here, because they are so 

 generally known as such. This is the northern tree-toad, or, as it 

 is called by others, the chameleon liyla. Hi/la is the scientific 

 appellation of the genus to which all the true tree-toads have 

 been referred; and our common tree-toad is called H. versicolor, 

 from the w 7 ell-known fact that it possesses the power of varying 

 the shade of its skin. At certain times this little toad is of a very 

 pale ash color above, variegated with marbled markings, while 

 beneath it is nearly white, and the low^er and inner sides of the 

 thighs are of a beautiful yellow, with a few darker maculations. 

 From this livery I have seen it slowly pass through a pale olive 

 shade to one of a rich snuff-brow r n, with the mottlings on the 

 back nearly black, while very little change was to be observed 

 upon the lower parts. This all happened when the creature was 

 placed on a very dark and wet piece of pine bark in a closed jar. 

 An hour later, when I returned to look at him, he, with another 

 individual of the same species, had crept beneath the bark, and 

 were close against the glass, and by this time had assumed the 

 palest possible tint of gray, with the marbling very distinct 



