f 



260 ZOOLOGY. 



a jelly ; in the latter as two long, perfectly cylindrical cords erf trans- 

 parent jelly, with the eggs inclosed at regular intervals. The development 

 of the egg takes place much as in the case of the frog, already referred to ; 

 the tadpole, however, never attains to a great size, and the transformations 

 are completed in much less time. A difference in the amount of metamor- 

 phosis is also observed. 



While the embryonic fin of the hind foot is permanent in the water-frog, 

 and disappears but partially in the tree-frog, in the toad it vanishes 

 entirely, leaving the hind feet cleft to the base. Of the true genus Bufo, 

 with simple toes and a distinct tympanum, there are several species known 

 in the United States, but one, however, B. americanus, occurring in the 

 northern portions. A common European species, B. viridis, is seen in pi. 

 90, fig. 1. PI. 81, fig. 36, represents a variety of this, known as B. 

 calami ta, with a yellow dorsal stripe. The genus Engy stoma is also an 

 inhabitant of the southern parts of the United States. It is distinguished 

 from Bufo by the absence of a tympanum, and the rather long and slender 

 toes. PI. 90, fig. 2, rei)resents a species, E. ovale, from South America. 



As already observed, the most conspicuous character of the sub-order 

 Phrynaglossa is to be found in the entire absence of a tongue : this organ 

 existing, in greater or less development, in all the other aiijoura. A second 

 character, no less important, is to be found in the fact that the Eustachian 

 tube is single, and situated on the posterior median portion of the palate. 

 In the others, there are two, one on each side, sometimes at a considerable 

 distance from each other. There are but two genera included in this sub- 

 order. 



The genus Dactelythra is provided with teeth in the upper mandible, but 

 not on the vomer. The Eustachian orifice is of considerable size at the 

 posterior part of the palate. The toes are simple, four anterior and five 

 posterior, the three first of those on the hind foot encased by their terminal 

 extremity in a horny, thimble-like process. The single species, D. capensis 

 (pi. QO, fig. 3), is a native of South Africa. 



With the same ordinal characteristics as the last the genus Pipa is 

 distinguished by the entire absence of teeth, the small Eustachian orifice 

 situated nearly in the centre of the palate, and the four anterior toes, each 

 subdivided into four small branches at the terminal extremity. The hind 

 feet are entirely palmated. The most singular feature in the history of the 

 single species P. arnericana {pi. 90, fig. 4) is to be found in the manner in 

 which the eggs are developed. The eggs, as laid by the female, are placed 

 upon her back by the male, who fertilizes them there with his seminal fluid. 

 The eggs, adhering with great tenacity to the back of the female Pipa, 

 produce a peculiar irritation, which results in the evolution of a mem- 

 branous or cellular matter, which, g owing round the eggs, envelopes them 

 completely. Here they undergo a . their changes from the embryo to the 

 larva or tadpole, and thence to the perfect frog; emerging, after the lapse 

 of about eighty days, in a fully formed and tailless state, although exceed- 

 ingly minute. The Pipa is an inhabitant of various parts of South 

 America, especially of Guiana and Brazil. 



