278 INEZ L. WHIPPLE. 



The method of change of respiratory habit necessitated by the 

 transition from one median to the other is interesting. When a 

 Dicmyctyhts which has been breathing air is submerged in water, 

 bucco-pharyngeal respiration of water begins almost at once. 

 Amblystomas, being less thoroughly aquatic, postpone this change 

 of habit for a longer or shorter time. The nares in this case are 

 at first tightly closed and if the animal is kept submerged for 

 only a few minutes it may not establish aquatic respiration at all. 

 When a specimen which has fully established the aquatic habit 

 of respiration is taken from the water there is evinced more or 

 less mechanical difficulty in reestablishing the aerial habit. This 

 difficulty arises from the fact that the nasal passages are filled 

 with water which must be removed before rapid, unimpeded res- 

 piration of air can occur. The efforts to do this involve forced 

 and greatly exaggerated depressions of the floor of the mouth, a 

 device which may prove efficacious in two ways, first, by draw- 

 ing the water from the nasal passages into the mouth, and sec- 

 ond, by drawing from the lungs a supply of air which can be 

 used to force the water out of the nasal passages through the ex- 

 ternal nares. The transition from aquatic to aerial respiration 

 may thus involve much effort and a considerable loss of time. 

 I have observed specimens of Diemyctylus to consume ten min- 

 utes or more before perfectly normal aerial respiration was estab- 

 lished. Amblystomas make the transition more quickly. 



In connection with this mechanical difficulty of rapid transi- 

 tion from aquatic to aerial respiration, some lunged salamanders, 

 notably Diemyctylus, have acquired for use when in the water a 

 modification of the ordinary method of pulmonary respiration. 

 Frequently air must be taken into the lungs during the brief 

 period when by a rapid swimming to the surface, sufficient mo- 

 mentum has been acquired to force the head for an instant out 

 of the water. It is evident that under these conditions the nos- 

 trils are utterly useless as air passages, as they are filled with 

 \vater. Moreover, even if they were empty of water, or could be 

 emptied in so brief a time, the ordinary method of drawing in air 

 through such narrow passages is far too slow to be made use of 

 here. The method employed is, therefore, a quick, gulping 

 motion by means of which the water in the mouth is replaced by 



