364 H. D. REED 



It has been stated above that the complete absence of the col- 

 umella in Siren points to an extended period of terrestrial exist- 

 ence further back in its phylogeny. A study of the general 

 anatomy of this form by H. H. Wilder ('91) led him to the same 

 conclusion. In summarizing his work he observes concerning the 

 phylogenetic relations of Siren: "I am fully convinced that it 

 has once possessed a terrestrial existence and been driven back 

 to an aquatic life during the struggle for existence, similarly to 

 the case of the Axolotl. . . . But unlike the Axolotl, which 

 has simply repressed the later stages and represents still a fairly 

 typical larva, the Siren-form has been modified by the influence 

 of external conditions during a much longer period of time. 

 . . ." While the position assigned Siren in plate 6 is tentative, 

 although indicated by all of the available structural evidence, 

 its position within the legion seems unquestionable. 



The case of the Cryptobranchidae, so far as the sound-trans- 

 mitting apparatus is concerned, must be adjusted by the evi- 

 dence offered by the columella alone, since the operculum is 

 wanting. The fenestral plate is single, possesses only suspen- 

 sorial connections, and is formed by the spreading of extraotic 

 material over the outer surface of the fenestral membrane, in 

 which respect it agrees with the columella of the amblystomids, 

 tritons, and Salamandra, and is at variance with every other 

 known group of urodeles. This feature, being in such sharp 

 contrast between the two great groups of urodeles, it very clearly 

 allies the Cryptobranchidae with the amblystomid division or 

 legion I. The position of this family within the legion is inter- 

 preted as a direct offshoot of the amblystomid stem. 



The fenestral plate of the Cryptobranchidae with its suspen- 

 sorial connections only, is of the type found in aquatic species 

 or during the larval period of terrestrial forms and does not of 

 itself indicate whether these animals are primitively or second- 

 arily simple. During the transitional period from the fish-like to 

 the terrestrial amphibians, the skeletal remains, and especially 

 the restorations, denote a lumbering mode of locomotion in 

 which the body was scarcely elevated above the substratum 

 upon which it probably rested during inactive intervals. What 



