The Lateral Nasal Glands of Amphiuma. 163 



stricter or dilatator nasal muscles. On the other hand, the extensive 

 range of variation in both the number and the length of the gland 

 tubules, as well as the actual evidence of atrophy which was found 

 in the case of one of the tubules, indicates that the glands have lost 

 their functional importance in Proteus, and that they are in a more 

 or les? degenerate state. If, now, this function was originally asso- 

 ciated with that of the constrictor and dilatator muscles, the failure 

 of the latter in Proteus is quite consistent with the condition of the 

 glands. The absence of the muscles and the degenerate state of the 

 glands are both facts which will prove of importance in the final 

 consideration of the functions of these parts. 



As to the other pcrennibranchs, in both Necturus and Siren there 

 is complete failure of both the external nasal glands and the con- 

 strictor and dilatator muscles ; and Axolotl, if indeed this permanent 

 larva is to be considered in this group, is described by Bruner 

 as possessing the rudiments of both glands and muscles, but, as 

 is the case with other salamandrids, these do not ap*pear until 

 the animal has nearly arrived at the adult stage. Typhlomolge, 

 another form which has been classed with the pcrennibranchs, was 

 shown quite conclusively by Miss Emerson, '05, to be a permanent 

 larva of some lungless form, probably closely related to the genus 

 Spelerpes. In view of this fact, one would hardly expect to find 

 external nasal glands or constrictor and dilatator muscles except, 

 possibly, in the very rudimentary condition which is characteristic 

 of that stage of the larva immediately preceding the transition into 

 the adult form. As a matter of fact, the single series of sections 

 through the head of a Typhlomolge which, through the kindness of 

 Miss Emerson, I had the privilege of examining, showed no evidence 

 whatever of any of these structures. Too much dependence should 

 not be placed upon this observation, however, as the specimen from 

 which the series was made was somewhat imperfect in the region of 

 the ex^rnal nares. 



Cryptobranchus allegheniensis possesses well developed constrictor 

 and dilatator muscles (Figs. 6 and Y), as may be readily demon- 

 strated either by dissection or by microscopic sections ; I have, how- 

 ever, been unable to find the slightest trace of any external nasal 

 glands. , ' 



