72 B. F. KINGSBURY. 



often grow : to enormous size, and undoubtedly are sexually ma- 

 ture while still possessing the larval form (Cope, Osborne 2 ), so 

 that the evidence is good that the Axolotl is a permanent larva. 

 A tendency to superlarvation seems to exist in other families 

 of tailed Amphibia. Spclcrpes larvae attain a length of 60 mm. 

 and I believe an age of two or three years before transforming. 

 Small adults are often of smaller size. Gyrinophilns porpliyritiais, 

 of the same family, attains a length of twelve centimeters before 

 undergoine transformation. The Museum of Cornell University 



O L> * 



contains such a specimen, together with adults fourteen centi- 

 meters long. 



Were the interpretation of Ncctitrns as a permanent larva to 

 be seriously accepted, there is no existing form to which it could 

 be related. As far as cranial characters go, the Plethodontidae, 

 (e. g., Gyrinoplilits] are temptingly adapted for serving as the 

 transformed kinsmen. However, one very important feature, ab- 

 sence of lungs, of course excludes them from consideration. 



The evidence that Necturus is a degenerate form, seems to me 

 very slight. There is no reason for regarding the absence of 

 pref rental, nasal, and maxillary as indications of degeneration. 

 The imperfect condition of ossification about the mandibular artic- 

 ulation also does not seem to me to indicate degeneration. The 

 chondrocranium is much "reduced" in extent; the trabeculae 

 delicate, the basilar plate imperfect, the nasal capsule incomplete 

 all of which suggests a reduction from the more usual urodele 

 type. But the place of the chondrocranium has been taken by the 

 bony elements of the skull. The parasphenoid surrounds the 

 cephalic end of the notochord, the frontals and parietals come 

 down to the parasphenoids to complete the side walls of the 

 cranial cavity, so that there is formed a very strong firm skull. 

 From one point of view, perhaps, were Nectnms regarded as a 



1> O3, Powers, J. H., "The Cause of Acceleration and Retardation in the Meta- 

 morphosis of Amblystoma ti^rinnm ; A Preliminary Report," Atn. Nat., Vol. 

 XXXVII., pp. 385-410. 1903. 



2 'oo, Osborn, H. L., "A Remarkable Axolotl from North Dakota," Am. A'af., 

 Vol. XXXIV., pp. 551-562. 1900. 



'01, f/>ii/., "On Some Points in the Anatomy of a Collection of Axolotls from 

 Colorado and a Specimen from Northern Dakota," Am. Nat., Vol. XXXV., pp. 

 887-897. 1901. 



