166 Inez Whipple Wilder. 



have several times noted that the closure of the nares during the act 

 of filling the lungs is not perfect, although usually it is so. 



It should be noted that the function of the nasal muscles is primar- 

 ily associated with the attainment of a terrestrial mode of life. Even 

 Cryptobranchus allegheniensis may not prove to be so decided an 

 exception to this statement as vi'ould at first appear in view of its 

 aquatic mode of life. I have not had the opportunity to study the 

 function of the nasal muscular apparatus in living Cryptobranchus. 

 Smith '07, reports however, that this species is somewhat burrowing 

 in its habits, and thus its power to close the nares must at such times 

 be of great value. Further, the species shows tendencies toward 

 adaptation to terrestrial life. The streams in which it lives are 

 liable to become almost dry. I have known specimens to live several 

 days entirely out of water during transportation, not even surrounded 

 by a wet packing, and to be normal and active at the end of the 

 journey. Since the systematic position of Cryptobranchus is more 

 or less of a problem, it is even possible that the presence of the nasal 

 muscles may be due to an ancestral terrestrial foi-m. 



As to the external nasal glands, their function also seems to be 

 a more generalized one than that suggested by Bruner, namely, the 

 lubrication of the edges of the nasal orifice to insure tight closure 

 during respiration. There is in terrestrial air-breathing forms a 

 great necessity for some device for keeping the thin delicate skin' 

 which covers the crescentic fold moist and pliable ; for this skin is, 

 owing to its location, constantly exposed to the drying effects of the 

 air as it moves in and out of the nasal cavity during bucco-pharyngeal 

 as well as pulmonary respiration. The acinous glands which are 

 abundantly developed for moistening the skin in other regions, are 

 wholly lacking here, probably because their large size would require 

 a greater thickness of skin than is consistent with the necessary flexi- 

 bility; but these external nasal glands with their large extent of 

 secreting surface are so deeply embedded that they cannot interfere 

 with the free movements of the skin, and their secretion is discharged 

 through slender ducts upon the surface of the fold, thus keeping the 

 region so thoroughly moist as to counteract the excessive drying effect 

 incident to the location. * 



