THE TYPICAL FROGS 2633 



hind-limbs are regularly barred, and the under parts unspotted. Two other Euro- 

 pean species, the one (R. iberica) from Spain and Portugal, and the other (/?. lata- 

 stei} from the neighborhood of Milan, differ by the spotted lower surface of the 

 body. Even the tadpoles of the whole of these more or less nearly-allied species 

 present differences by which they can be distinguished from one another. 



The common frog, whose habits may be taken as typical of the allied members 

 of the genus, is found in most parts of Europe, where there is a sufficiency of moist- 

 ure and shelter for its existence; the presence of water being essential during the 

 breeding season. All are probably familiar with the manner in which a frog swal- 

 lows air; but it is perhaps less generally known that if the mouth of one of these 

 creatures be kept forcibly open, death must inevitably ensue, owing to the impossi- 

 bility of breathing while in this state. The croaking of the frog is principally ut- 

 tered during the breeding season; and when large numbers of these Amphibians are 

 collected in a pond together, the volume of sound produced is considerable, and can 

 be heard from long distances, although it is nothing compared to that of the bull- 

 frog and many tropical species. Frogs subsist entirely on slugs, snails, insects, etc. , 

 swallowing large beetles whole, and devouring several at a meal. The frog cap- 

 tures its prey by suddenly throwing forward the tip of its tongue, which is invested 

 with a viscid secretion, upon the insect or slug, and then as quickly withdrawing it 

 to its normal inverted position. So rapid is the whole movement, that it requires a 

 sharp eye to detect it; the insect seeming to disappear as if by magic. " Frogs re- 

 tire," writes Bell, "on the approach of winter to their hibernating retreats, where 

 they pass the dreary season in a state of absolute torpidity. This is generally in 

 the mud at the bottom of the water, where they are not only preserved, though at 

 low degree, but also secured from external injury. Here they congregate in multi- 

 tudes, embracing each other so closely as to appear almost as one continuous mass. 

 On the return of spring they separate from each other, emerge from their places of 

 retirement, and recommence their active life by exercising the important function of 

 reproducing their species." During the breeding season a warty protuberance is 

 developed on the thumb of the male to assist in holding the female; and in some 

 foreign species the whole fore-arm becomes enlarged at this time. The spawn is de- 

 posited at the bottom of the water, but soon rises to the surface in the well-known 

 glairy masses; and in due season the tadpoles make their appearance. During the 

 tadpole stage frogs are devoured in large numbers by newts and the smaller 

 fishes; while in the adult condition numbers fall prey to the weasel and polecat, the 

 heron and other wading birds, and the common snake, whose food is almost entirely 

 composed of them., Although the common frog is to a large extent aquatic, it is 

 much less so than the edible species, which inhabits indiscriminately running or still 

 waters, the borders of rivers, rivulets, or streams, lakes or ponds, salt or fresh 

 marshes, or even ditches and pools of water. Owing to the presence of the external 

 sacs, the croaking of the male is louder than in the common frog. Both species, 

 like all the more typical representatives of the genus, progress on land by means of 

 leaps; while in water they swim with the hind-limbs alone. 



Compared to the bullfrog (R. catesbyana} of Eastern North America, repre- 

 sented in the figure on p. 2624, the European frogs are mere dwarfs; but the largest 



