12 BULLETIN 34, UNITED STATES NATIONAL MUSEUM. 



but in the Salientia the spermatozooids are discharged on the ova after 

 leaving the body of the female. (Plates 18, 19, 32, 42.) 



The alimentary canal in the Batrachia is simple, since it is not highly 

 specialized into distinct parts. The liver is large and is divided into a 

 varying number of lobes, which are especially numerous, and arranged 

 like a roll of coins in the Creciliidse. The gall-bladder and pancreas 

 are present. The teeth are not implanted in alveolse, and are in the 

 recent forms more or less pleurodont. 



LARVAL CHARACTERS. 



In the course of the growth of a batrachian there is always a period 

 which follows the freedom of the embryo, in which there are structures 

 for securing respiration in the water. These gills differ from those of 

 fishes, in that the fringes in which the blood is aerated stand on fleshy 

 processes of the branchial arches, and not directly on the arches them- 

 selves. Similar structures are found in the preliminary stages of 

 some fishes. During this stage the tail is more or less modified as a 

 swimming organ, and the condition of the skull differs materially in 

 character from that of the adult. In the tailless or anurous Batrachia 

 the limbs do not appear until this period has nearly closed, while in 

 the tailed or urodele order the limbs appear almost immediately after 

 the gills. Besides these transitional characters, theUrodela possess in 

 their early larval condition a long process in front of the first gill on 

 each side, which is termed a balancer. This remains in a few abnormal 

 cases in salamanders, but is permanent in the suborder of the caecil- 

 ians or worm-like Batrachia. A similar process exists in the larva of 

 the frogs of the genus Xenopus^ which resembles superficially a siluroid 

 fish ; but in the Salientia generally the balancers are wanting. 



The gills in the Salientia (frogs, toads, etc.) are soon concealed by a 

 growth of the skin, which leaves a small orifice for the discharge of 

 water from the pharyngeal cavity. In one group of these animals this 

 opening is on the middle line below, but in the great majority it is 

 single and is situated on the left side. 



The changes undergone by the skull in the metamorphosis are much 

 more important in the Salientia than in any other order, and are treated 

 of under the head of that order. 



The eggs of Batrachia are always deposited in the water or in damp 

 places. In a few instances the young do not seek the water, and in 

 one species {Salamandra atra) they are born free from the egg. 



Under the head of the Salientia will be found a table of the various 

 modes in which the eggs and larvae of those animals are deposited and 

 cared for prior to maturity. 



Under the respective orders the descriptions of their characteristic 

 peculiarities of development will be found. (Plates 30, 44, 78.) 



