100 THE ROYAL SOCIETY OF CANADA 



tion, immediately followed, as the head returns under water, by a 

 forcible swallowing motion, by which air is forced from the mouth 

 partly into the lungs and partly out through the nostrils. There is 

 abundant visible proof that air has entered the lungs, in the increase 

 of girth and especially in the immediate increase in buoyancy. The 

 authoress gives many other details regarding the hydrostatic habits 

 of Diemyctylus. On the other hand she has never observed Necturus 

 to float except upon one or two occasions when the water had become 

 very foul: "occasionally it will swim to the surface and take in air 

 through the mouth by a gulping motion," but again there is no evi- 

 dence that any of this air is passed into the lungs; it escapes through 

 the mouth and gill slits as the animal sinks slowly to the bottom. 



Kneeland (1859) kept a Necturus for an hour out of water during 

 which time it occasionally opened its mouth "as if to swallow water 

 or air." I have also seen this act of gasping out of water but it is not 

 accompanied or followed by any visible act of swallowing. In June 

 1858 Kneeland placed two individuals into an aquarium in company 

 with half a dozen minnows. The fish were frequently seen nibbling 

 at the expanded gills of the Necturus. In about ten days the branchial 

 fringes had all been nibbled away. The fish were then removed and 

 in the course of six months the fringes had been regenerated to half 

 their normal size. The temporary loss of the gills did not incom- 

 mode them in any wa}^ since the general cutaneous respiration re- 

 mained unimpeded. This observation I have indirectly confirmed 

 by ligaturing and extirpating the external gills, an operation which 

 has no apparent elïect on their habits or activities. The gills regen- 

 erate in due course. 



The lungs of Necturus are like the air-chambers of Nautilus. 

 A floating Nautilus is a moribund Nautilus, and it is doubtless the 

 same with Necturus. More observations, accurately timed and 

 recorded, are required to settle various questions which arise in con- 

 nection with the behaviour of Necturus in captivity. It is a matter 

 which consumes much time, so rarely does anything happen to dis- 

 turb its equanimity when resting quietly at the bottom. One cause 

 of the floating of fasting Necturus in arh'erse surroundings is the 

 formation of gas in the intestine, a pathological condition.. Finally 

 when Necturus casually swims to the surface and protrudes its snout, 

 whether the mouth be opened or not, there is no increase in buoyancy 

 nor in girth. 



In the summer time frogs can survive a moderate duration of 

 immersion; in winter they voluntarily submerge themselves and 

 hibernate under water, becoming inactive. A male frog (Rana 

 virescens) was placed in a shallow dish covered with a perforated zinc 



