258 ZOOLOGY. 



simplest and most efficacious way is to tie three large hooks back to back, 

 and affix a piece of red flannel, at which, especially in bright, sunshiny 

 weather, the frog will often spring with great avidity, and thus hook itself. 

 Of the 16 genera into which this family is divided, but three are natives of 

 North America, one of them being peculiar to it. The first genus, Rana, 

 or true frog, has the large fleshy tongue divided more or less posteriorly 

 into two cornua or branches, capable of considerable motion, and used in 

 capturing the food of the animal, by which character it is distinguished 

 from all the other genera. Species of this genus are quite numerous in 

 North America, one of them, Rana pipiens, known as the bull-frog, 

 attaining to an enormous size, and celebrated for the loud bellowing audible 

 at a great distance. Individuals have been seen that measured 22 inches 

 between the ends of the extended extremities, and even this size has been 

 exceeded. The next largest species is the R. fontinalis, distinguished 

 from the first by the presence of a fold of skin running along the side of 

 the animal. The other species are not very conspicuous excepting the 

 Rana syhatica, or wood frog, an animal often Ibund in damp woods 

 among the leaves, and exciting attention by its yellowish color, and bl^ck 

 stripe on the sides of the head passing through the eyes, as also by the 

 extreme agility of its movements. The R. temporaria of Europe {pi. 81, 

 Jig, 34) is exceedingly like it, the principal difference lying in a smaller 

 tympanum. Another European species, R. escule.nta, is shown in pi. 90, 

 fig. 5. This, like all the true frogs, or RancB, has a membrane between 

 the hind toes to assist in aquatic propulsion. The number of eggs laid by 

 the frogs is very considerable, in some cases amounting to several thou- 

 sands. They are generally deposited around some aquatic plant enveloped 

 in a gelatinous mass. When the ova are ready for exclusion, the male 

 mounts upon the back of the female, and as the eggs are discharged ejects 

 a small quantity of seminal fluid into the water where the operation takes 

 place — this sometimes occupying days and even weeks, during the whole 

 of which time the pair thus remain attached. The egg after passing 

 through the embryonic changes appears as a larva, all head and tail, with 

 simple entire gills which soon disappear, to be followed by others of more 

 complicated structure, situated within the cavity of the body as in fishes. 

 After a certain length of time the hind legs begin to appear, and still later 

 the forelegs are found to exist, fully formed beneath the skin, ultimately to 

 burst forth. The tail then disappears by absorption, this taking place very 

 rapidly. A remarkable internal transformation takes place during these 

 external changes, from tbe herbivorous tadpole to the carnivorous frog. 

 The reproductive history of ;iearly all the Batrachia anoura is very similar 

 to that just described, with special modifications, to be referred to under 

 the proper head. 



The genus Scaphiopus, with much of the appearance of a toad, is yet 

 distinguished by the teeth in the upper jaw. There is a cartilaginous pro- 

 cess on the hind foot, serving the purpose of a shovel in excavating the 

 holes in which the animal dwells. The toes are palmated, and the tongue 

 nearly entire. Cystignathus is well distinguished by the entire absence of 

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