RANK OF NECTUKUS AMONG TAILED BATRACHIA. 73 



permanent larva, the fact of superlarvation might itself be re- 

 garded as an indication of degeneration. The failure to undergo 

 transformation could be interpreted as, in a sense, arrested de- 

 velopment --a form of degeneration. 



The evidence that Necturus is a low form, seems to me quite 

 as tentative in character as that in favor of Ncctnrus as a perma- 

 nent larva. Cope has placed Nectnrns and Proteus in an order, 

 the Proteida, as the lowest of the tailed Amphibia, giving as the 

 critical character the presence of an intercalary bone, relating 

 it to the extinct Stegocephali. Examination of series through 

 the skull, however, 1 shows no such bone present. Apparently 

 what was regarded by Cope as an Os intercalare (Epioticum) is 

 the backward extension of the caudal ossification of the ear cap- 

 sule (o.pisthotic ?). From examination of figures (no specimens 

 of Stegocephali have been seen by me), the intercalary seems to 

 be a dermal bone and not a part of the ossification of the ear 

 capsule. The ossification in this region is peculiar, consisting, in 

 Nectnrns of a cephalic ossification (prootic?), and a caudal (opis- 

 thotic ?) which perhaps spreads to it from the exoccipital arch. 

 The homology of the ossifications in theear capsule in Amphibia 

 as elsewhere, I judge to be in a very unsatisfactory state at pres- 

 ent, and even though the Os intercalare belonged to the bones 

 of the ear capsule, it would not be of value in determining the 

 rank of Necturus until more is known of the mode of ossification 

 in other tailed Amphibia. 



So far as the skull is concerned, the real characters which 

 must be considered in placing Nectnrns low among tailed Am- 

 phibia, are, I believe, the same as those which, differently inter- 

 preted, afford evidence of Nectnrns as a permanent larva, /. e., 

 the absence of prefrontal, maxillary, etc. If we interpret the 

 larval stage as representing in ontogeny a stage through which 

 the species has passed in its development, then larval characters 

 can be regarded as primitive, and Nectnrns as a primitive form. 

 Aside from the general question of " Ontogeny an Epitome of 

 Phylogeny," such an interpretation of the larval stage is not 

 entirely satisfactory ; there are some features that suggest that 



'There were included specimens 16 mm. long up to an individual 20 cm. in 

 length. 



