No. 470] 



HABITS OF NECTURUS 



127 



When these animals are retained in aquaria tliey arc frc(]uciitly 

 observed to thrust their snouts ahove the water, open ilir mouth 

 widely, and then return to tli(> hottoni wiicrc* tlicv sodti expel 

 air both throucrh the n-ill shts and from the m.)iith. It would 

 thus seem that while tli<- hnmclii-r aie the chief menus of ivs|)ira- 

 tion the lungs play cousideraMe part. Kueelaiid i o!»i maile some 



minnows, varying in size from two to three iiiehe-.. The fish 

 were frequently seen nibbling at the expanded iiil!.> of the rej)- 

 tiles, whieh as often suddenly darted from their onhnai v state of 

 repose, attempting to seize the hsh, whieh they never succecvled in 

 doing. In about ten days the nienobranehs had notliiuu li>ft of 

 the gills but the almost bare cartilaginous supports, with only 

 here and there a branchial fringe. The fish were then taken 

 out, and the branchial fringes began to grow a'^aiii. and in the 

 course of six months had re-aiued about half their nonual size. 

 He ha<l ^^atehed these teotih- for tuo siunmeis, and no nmilar 

 falling of tlu-uiiU r^rv took place. that it a p peat- in the pre^- 



patholou-icalaud not a natm-al phenomenon. In either case this fact 

 st'cms inKM'cstinu from a physiological j)oint of view, as bearing 

 upon the re^piratorv oriran^ of these reptiles. He had ascertained 

 c\j)(-rimcutallv that they survive out of water about four hours, 

 showino- tliat their j)ulmonary sacs, or lungs, are not alone suf- 

 ficient for the maintenance of respiration. In the present in- 

 stance, though th(>ir pulmonary sacs were the principal respira- 

 torv orcrans, the aninu,l> di.l n..t apparently suH'er. . . . 



"The (piestion arises, whv arc tluvs(> lunu-s apj.arently suflicicnt 

 for respiration in tiie water and not in the air. though tlic ivsi)ire(l 

 element be in l)oth cases the same? As there is no evidence of 

 internal gills, the reason must be that in the air the branchial 

 tufts from dryness are unfit for circnhitin<: flic l)loo<l, the com- 



for the ae.aii<.n of ihr blood, and the animal dies. I,, the uater. 

 however, even though the branchiic, as in this case be useless, 

 the cutaneous respiration is unimpeded and with the pulmonary 



