RANK OF NECTURUS AMONG TAILED BATRACHIA. J I 



can only be given in general, as my notes fail me for details. 

 The nerves especially indicated are the V. and VII., and the 

 muscles, the muscles of the jaw, hyoid, and branchial apparatus. 

 I regret also that the table is incomplete in the important point 

 the relations of the branchial arches so that I cannot state def- 

 initely whether there is complete correspondence, i. e., whether 

 the relations of the second basibranchial and the three epibranch- 

 als, are the same or not in the two forms. 



As cranial characters peculiarly associated with the larval state, 

 are to be mentioned : 



1. Presence of a pterygo-palatine and absence of a vomero- 

 palatine. 



2. The absence of prefrontals (and nasals). 



3. The absence of a processus pterygoideus quadrati (cart.). 



4. The absence of a maxillare. 



5. Presence of an operculare (spleniale). 



All of these characters Ncctnrns possesses, and in addition, 

 closely resembles the larval Spclcrpes in (a) the state of ossifica- 

 tion of the quadrate, (b] the ossifications in the mandible, and (c) 

 less clearly, in the rudimentary development of the nasal capsule. 



Four possible interpretations of the structural characters men- 

 tioned above, and the systematic position of Ncctnnis, may be 

 made, (a) Ncctnms is a permanent larva, ($) it is a degenerate 

 form, (c] It is a generalized or low form and (<;/) the possibility 

 should also be considered that Necturns owes the structural char- 

 acters of the skull in which it resembles larval urodeles, to the 

 fact that both are living under very similar conditions of environ- 







ment--that these characters are in some way connected with 

 the branchial respiration and aquatic life of the form, and repre- 

 sent an adaptation, and adjustment to the environment. 



In favor of Necturus as a permanent larva stand the larval re- 

 semblances enumerated above. Circumstantial support for this 

 view is also given by the generally accepted fact that the gilled 

 Axolotl (Siredon pisciformis) is a permanent larval form of a 

 species belonging to the genus Amblystama. 



The statement in Cope's Batrachia, still holds good, I think. 

 No one has accomplished the transformation of the Mexican 

 Axolotl. On the other hand, the larvae of Amblystoma tigrininn 



