INTRODUCTION. XXIX 



When first seen they arc fleshy buds. These elongate, and the rounded 

 extremity show.s signs of dividing into two. One of the two becomes the 

 inner finger; on the (uitside of the other the third linger pushes out, iind 

 beyond the latter toward the wrist the fourtli. Tlie hind limbs a})pear 

 in similar manner. A single toe is formed of the inner lobe, the outer 

 being one, or becoming two, three, or four according to the genus. In 

 certain genera there is much variation in regard to mind)er of digits; 

 Proteus is a g(jod instance; Amphiuma is another. Of twenty-six spec- 

 imens of Ann)hia}iia tridacti/Jum, twenty have three toes, the normal 

 number, to each foot, and among the others occur the following one 

 has one toe on each hind foot; one has one variations: to the right hind 

 foot and two to the left ; two have single toes on the right fore foot ; another 

 has one, and still another has two on the left fore foot. 



tialuiiiandra afra is one of the cases in which the young are hatched in 

 the oviduct. The eggs of some are fertilized in the oviduct during copula- 

 tion; those of others are thrown free into the water to come in contact witli 

 the sperm emitted by the male at the same instant. According to accounts 

 recently published by M. Gasco, the female Axt)lotl finds the spermatophore 

 which has been deposited by the male, and placing the cloacal opening over 

 it introduces a jwrtion, and thus secures fertilization. It is generally con- 

 ceded that the males are more numerous than the females of species of this 

 order. One of the oddest forms is Plenrodcles, in which the, ribs extend 

 through the skin on the flank. 



The Uroihla belong to the temperate regions of the ]^orthern hemis- 

 phere. Most of them are found in North America. Tlie hvrgest known 

 is tlie Megalobatrachus of Japan. Of the North American, the largest is 

 the aquatic genus Meiiojioma* 



The Anura or tailless Batrachia have short bodies and short necks. The 

 vertebra* are few, and in body or neck comparati\ely immovable, (ien- 

 erally the hind limbs are longer and stronger. There are four digits on the 

 hand and five on the foot. Except in a few sj)ecies of those living in trees, 

 there are no webs between the fingers. BJiaeophoras is the most marked 

 exception; it has such extensive webs between fingers and toes as to be able 

 by their aid to sail long distances in the manner of flying lizards or squirrels. 

 Webs are common to the aquatic species, as in frogs, Banidce. Terrestrial 

 frogs are more or less completely without the palmation. In Cystignathidie 

 the toes are free. Pi]}a, the Surinam Toad, one of the group Aglossa, or 



*Ci'ypiobi-anchius. 



