À Contribution to tlie Anîitolny of Siien liicertina. 



693 



o 



Siren 



1 



O 



iSiredon 



If I might compare the conditions of the two animals by a dia- 

 gram it would be somewhat as follows: 



In this diagram, i re- 

 ^ presents in each case the 



ancestral perennibranch, 

 2 the successful terre- 

 strial form and S the mo- 

 dern form. 



à The dotted line repre- 



sents the boundary be- 

 tween aquatic and ter- 

 restrial life {A. T). Whe- 

 ther Siren could, at the 

 present day, under fa- 

 vorable conditions, be again transformed into its former terrestrial 

 form , as in the case of the Axolotl , must be settled by experiment. 

 From the anatomical side, however, it looks extremely doubtful. 



The facts upon which the above conclusions are based, are as 

 follows : 



a) That Siren possessed formerly a terrestrial life, we have the 

 facts of numberless correspondences in anatomical structure 

 with that of Siredon, and particularly the occurrence of inter- 

 maxillary glands. 



b) That it is at present more degenerate than Siredon, may be 

 concluded form the greater proportionate length of the body, 

 the head having similar proportions ; the absence of hind limbs ; 

 and the relation of the cartilaginous elements in the nose, 

 which shows the nasal capsules separated from the internasal 

 septum. 



