384 THE ZOOLOGIST. 



ON THE YAWNING OF FISHES AND OF OTHER 

 VERTEBRATES. 



By Alfred Heneage Cocks. 



Mr. Richard Elmhirst's observations (ante, p. 321) " On 

 the Yawning of Fishes " and of other Vertebrates, though very- 

 interesting, are surely not a new discovery. It is now fully 

 forty-six years since I set up some small fresh-water aquaria, 

 wherein in the course of time a considerable number of fish were 

 under observation, representative of about two dozen species, 

 and I have not infrequently seen fish yawn, but made no notes as 

 to which species were seen to do so, because it never occurred 

 to me until now, on reading Mr. Elmhirst's remarks, that this 

 action was otherwise than a well-known habit common to most, 

 if not all, vertebrates. 



My conviction is that all the two dozen or so species did 

 this, except perhaps Lamperns and Fringe-lipped Lamperns. I 

 have elsewhere seen various species of sea-fish yawn. For 

 several years previous to starting aquaria I must have been 

 aware that at least a few of the more familiar domestic mammals 

 yawn. During the years that have since passed I have seen so 

 many vertebrates of all classes and of so many orders yawn that 

 I cannot doubt that it is a general, even a universal, habit, and 

 there must be numbers of observers who have watched animals 

 in captivity, in the London and other zoological gardens, who 

 can easily cap my very imperfect recollections. It is natural to 

 suppose that animals in captivity (even in comparatively roomy 

 quarters) would yawn more frequently than those at liberty, and 

 at any rate one has with the former a better chance of observing 

 the act. 



With regard to Birds, I venture to generalize, and to declare 

 my belief that there is no exception to the axiom that all birds 

 yawn. I know that many Reptiles and Batrachians yawn, and 

 it seems unlikely that there are any exceptions among these 

 classes also. 



