INTRODUCTION. XX IX 
When first seen they are fleshy buds. These elongate, and the rounded 
extremity shows signs of dividing into two. One of the two becomes the 
inner finger; on the outside of the other the third finger pushes out, and 
beyond the latter toward the wrist the fourth. The hind limbs appear 
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 number of digits; 
Proteus is a good instance; Amphiuma is another. Of twenty-six spec- 
imens of Amphiuma tridactylum, 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. 
Salamandra atra 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 with 
the sperm emitted by the male at the same instant. According to accounts 
recently published by M. Gasco, the female Axolotl finds the spermatophore 
which has been deposited by the male, and placing the cloacal opening over 
it introduces a portion, and thus secures fertilization. It is generally con- 
eeded that the males are more numerous than the females of species of this 
order. One of the oddest forms is Plewrodeles, in which the ribs extend 
through the skin on the flank. 
The Urodela belong to the temperate regions of the Northern hemis- 
phere. Most of them are found in North America. The largest known 
is the Megalobatrachus of Japan. Of the North American, the largest. is 
the aquatic genus Menopoma.* 
The Anura or tailless Batrachia have short bodies and short necks. The 
vertebrae are few, and in body or neck comparatively immovable. Gen- 
erally the hind limbs are longer and stronger. There are four digits on the 
hand and five on the foot. Except in a few species of those living in trees, 
there are no webs between the fingers. Rhacophorus 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, Ranide. Terrestrial 
frogs are more or less completely without the palmation. In Cystignathide 
the toes are free. Pipa, the Surinam Toad, one of the group Aglossa, or 
* Cryptobranchus, 
