98 THE ROYAL SOCIETY OF CANADA 



in an insecure vessel of water, they will always escape from it over- 

 night and be found dead in the morning. Under other circumstances 

 I have occasionally seen them open their mouths above the surface; 

 this yawning movement may be a reaction to the dearth of food, 

 but it has nothing to do with functional inhalation, the ensuing air- 

 bubbles being discharged through the gill-clefts or mouth. When 

 exhibited before a class of students, the gills are sometimes moved 

 actively, at other times relaxed, but never is any attempt made to 

 reach the surface, if the container is not too small. 



Eycleshymer (1906) states that when the animals are retained 

 in aquaria "they are frequently observed to thrust their snouts above 

 the water, open the mouth widely, and then return to the bottom 

 where they soon expel the air both through the gill slits and from the 

 mouth." No evidence is brought forward to show that any of the 

 air enters the lungs through the diminutive glottis.^ When swim- 

 ming about in an aquarium they more frequently thrust the snout 

 above the surface without opening the mouth. From the passage 

 quoted above from Eycleshymer, it might be inferred that the be- 

 haviour of Nectiirus in the water resembles that of Diemyctylus. 

 This would be far from the truth. 



1 It is difficult to obtain direct evidence on this point as will appear from the 

 following experiment. On February 12, 1914, a Necturus, which had been kept for 

 about three months in a large aquarium, was placed in a cylindrical glass jar, eight 

 inches deep, into the mouth of which was fitted, three and a quarter inches below 

 the surface, a perforated zinc disc. Aeration was effected by allowing water to 

 trickle from a tap into the funnel of a thistle tube which reached to the bottom of 

 the vessel; the water carried bubbles of air with it. Under these conditions the 

 Necturus remained in normal activity for the next ten days. Every night the tube 

 became slightly displaced by the nocturnal movements of the animal so as to stop 

 the aeration, but this had no ill effects. On February 22 the jar full of water was 

 transferred bodily to the aquarium and the latter was filled with water to a depth 

 of one foot, thus bringing it four inches above the level of the glass. The zinc disc 

 was removed and a minute afterwards the Necturus swam over the edge into the tank 

 without coming near the surface. It descended to the floor of the tank and walked 

 slowly round "it, gently respiring with its gills. After twenty-five minutes it swam 

 to the surface, protruded its muzzle into the air, opened its mouth and then de- 

 scended again, whereupon about half a dozen large air-bubbles issued from the right 

 gill-openings. Two minutes later it ascended once more to the surface, gulped in 

 air as before, descended and at once emitted a quantity of air-bubbles in rapid 

 succession from the right gill-openings. Henceforth the ventral surface of the trunk 

 no longer came into contact with the bottom, for the entire abdominal region was 

 arched upwards and it walked along the bottom in an awkward digitigrade manner. 

 During the next two hours it became active, swimming in mid-water, making fre- 

 quent excursions to the surface and protruding its muzzle but never again opening 

 its mouth nor emitting air-bubbles in its descent. Two young individuals were in 

 the tank at the same time, walking and resting protje on the bottom, not once rising 

 to the surface. 



