NASO-LABIAL GROOVE OF LUNGLESS SALAMANDERS. 17 



It is, however, an interesting fact that although bucco-pharyn- 

 geal aerial respiration may be necessary to the comfort of these 

 lungless forms, it is apparently not an absolute physiological 

 necessity. I made the experiment of confining individuals rep- 

 resenting several species of Desmognatkus, Plcthodon and Spclerpes 

 in wire cages which were kept immersed in running water with 

 no possible access to air for periods ranging from one to two 

 weeks in length. Although when liberated at the end of the ex- 

 periment they invariably swam immediately to the surface and 

 made the same vigorous efforts to escape that they had made 

 previous to the experiment, they showed no signs of impairment 

 Df physical function and continued to live afterwards in the ter- 

 rarium with no evidence of ill effects from the ordeal. They 

 were never discovered, however, to open the nares during the 

 confinement under water, or to show any other than the tightly 

 indrawn position of the floor of the mouth. 



Spelerpcs ruber, unlike most other lungless forms, shows a 

 a decided adaptability to aquatic life, and will live for weeks at the 

 bottom of an aquarium. In this cas* 3 . however, as in those of less 

 aquatic forms, under compulsory immersion, it is a significant fact 

 that not only were the external narcs apparently kept tightly closed 

 so long as the animal ivas under the water, but when finally 

 removed from the water and given access to the air t/ie resumption 

 of aerial bucco-pharyngeal respiration was immediate. 



The importance of these points for the present discussion will 

 be emphasized by comparison with the habits and behavior of 

 lunged salamanders under similar conditions. All of the lunged 

 salamanders have, in addition to pulmonary respiration, a bucco- 

 pharyngeal aerial respiration exactly similar to that of the lung- 

 less forms. When these lunged salamanders are placed under 

 water, however, although there is at first an attempt to exclude 

 the water from the nasal passages by closure of the external 

 nares, these are sooner or later opened and aquatic bucco-pharyn- 

 geal respiration is established similar mechanically to the aerial 

 method, though much slower. Usually there is the additional 

 difference that the water is expelled in part through the slightly 

 opened mouth, and in some few instances it has bee.n observed 

 to enter, also, through this channel as well as through the nares. 



