74 B - F. K1NGSBURV. 



it may be an adaptation. Furthermore, the "ancestor of the 

 Amphibia" would not be expected to be a form with a reduction 

 in the number of cranial bones, but rather the reverse. 



It would seem to me worth while to compare other parts of the 

 anatomy of Nectunts with the larval and adult forms of other 

 urodeles, to see whether there too similar larval characters are 

 to be encountered. 



What applies to Nectums applies to other gill-bearing forms. 

 If Siredon piscifonnis never transforms and is yet regarded as a 

 permanent larva, there is no good reason known to me why 

 Necturus should not be also considered in the same light. Of 

 the other forms Proteus, of course, agrees with Necturus in all 

 essential characters. Typldovwlge will probably resemble these 

 two when its skeletal characters are made known. Mr. Stej- 

 neger in his description of the form says that the maxillary bone 

 is absent and that an intercalary seems to be present. Mr. Lucas 

 is working upon the structural features of the skeleton. His 

 results have not been published as yet, I believe, and will be 

 awaited with interest. Siren has been regarded by Cope as a 

 larval form by retrograde metamorphosis. It resembles an 

 " ideal larva " in three of the characters given above -- absence of 

 a vomero-palatine, absence of prefontals, absence of a maxillare. 



I believe that the characters in the cranium of Nectnnts that 

 are discussed here are those that are also characteristic of the 

 larvae of many tailed Amphibia, especially so of certain forms 

 (family Plethodontidae), and that the acceptance of Nectnrns as 

 a permanent larva best explains at present these features. 



It is recognized that there are objections to be met. Necturus 

 probably can never be made to transform so that proof cannot 

 be furnished. There is no gill-less adult salamander whose larvae 

 Nectnrns so closely resembles as does Siredon piscifonnis the 

 Amblystoma larva. Ncctnrus, Protens and possibly Typlilomolge 

 are very closely alike in structural features, are sexually mature, 

 and occur in different parts of the world. One would not expect 

 them to be permanent larvae. 



An attempt to reach a closer decision leads to a study of 



metamorphosis in the Amphibia. 



CORNELL UNIVERSITY, ITHACA, N. Y., 

 October 12, 1904. 



