MOVEMENTS OF NECTURUS AND CRYPTOBIiANCH US. 



65] 



by him in Nectarus does not include the gross flap[)ing of the ex- 

 ternal gills. There is, therefore, an apparent textual discrepancy 

 between his account and mine, which will doubtless be cleared by 

 further independent observations. Bruner fortifies his statements 

 concerning the " biicco-pharyngeal mechanism " by a careful 

 description of the choanal valve of NectnTiis\ and he seems to 

 assign a preponderating role to the gill-clefts in the branchial 

 respiration of this genus. It is not altogether inconceivable that 

 in difterent parts of its climatic range, as well as under diverse 

 laboratory conditions, the several components of the respiratory 

 tract may vary in the relative frequency of their turns. The 

 behaviour of Cryptohranclius informs us that not every yawn is 

 an act of breathing. No contrast could be more realistic than 

 that between the restless, air-craving CryjytohrancJius and the 

 listless, gill-waving Neciv/nis when viewed at the right biological 

 moment in the splendidly appointed tanks of the New York 

 Aquarium. 



McGill University, Montreal, 

 October 10, 1920. 



