l8 INEZ L. WHIPPLE. 



The efficiency and readiness of this aquatic bucco-pharyngeal 

 respiration varies much with the aquatic habits of the individual 

 species, Dieinyctylus -riridcsccns, which is thoroughly aquatic, 

 showing one extreme, Amblystoma opacum * the other. 



After the establishment of aquatic bucco-pharyngeal respiration 

 in these forms, the removal from water to air is not accompanied, 

 as in the case of the lungless salamanders, by an immediate 

 resumption of aerial respiration. On the contrary there is often 

 much delay arising from the mechanical inconvenience of having 

 filled the nasal passages with water. It frequently requires much 

 gasping and several enormously exaggerated depressions of the 

 floor of the mouth as if an attempt were being made to draw an 

 obstruction from the nasal passages before finally unimpeded 

 aerial respiration through these is reestablished. 



With this difference between the respiratory habits of lunged 

 and lungless forms clearly in mind we are ready for the explana- 

 tion of the part which the naso-labial groove and glands play in 

 making possible the immediate resumption of aerial respiration 

 after its temporary interruption by submersion in water. 



When the nares are closed, there remains, externally, a slight 

 depression, the floor of which is formed by the fold which closes 

 the orifice. When the snout is thrust out of water there is a 

 tendency, as the water drains from the surface of the head, for 

 each nasal depression to retain some of it. Thus it would be 

 expected that the opening of the naris for the resumption of aerial 

 respiration would allow this water to enter the nasal passage, 

 especially as the depression of the floor of the mouth in the act 

 of inhaling would draw in the water first of all. As a matter of 

 fact, however, nothing of the sort occurs. When the snout is 

 thrust out of water, the accumulation of the fluid in the nasal 

 depression is only momentary. With the opening of the naris 

 through the drawing back of the crescentic fold, the last vestige 

 of this drop of water disappears ; and, although the whole sur- 

 rounding skin is wet, the nasal depression and the naso-labial 



1 In a previous article on the Vpsiloid Apparatus of Urodeles (BIOLOGICAL BULLE- 

 TIN, Vol. X., No. 6), I have shown that this species, which has been erroneously sup- 

 posed to be lungless, really has well developed, functional lungs. In the same article is 

 given also a more complete account of the respiratory habits of the lunged salamanders. 



