51 



the second year he becomes a chilly being, and substitutes 

 flannel and great coats for the nankeens and cottons with 

 which, on his first arrival, he boasted he could resist the 

 cold easier than the better clad inhabitants. I have before 

 said, that we want accurate observations on the temperature 

 of the cold-blooded animals, with the exception of those of 

 Newport on insects. Dr. Davy found that the tempera- 

 ture of reptiles and fishes was only a few degrees above 

 that of the medium in which they lived. His observations 

 are however few, and, although made with his usual accu- 

 rate attention to all the concomitant circumstances, are 

 under such few varieties of circumstance, as to afford com- 

 parative little information. There is one observation made 

 by him on the temperature of the Bonito (Thynnus 

 Pelamys) which leads to the suspicion, that if the tem- 

 perature of fishes were examined under a variety of 

 oircumstances, although no results so remarkable as he 

 found in that fish would be found in others, yet, that 

 at certain periods, much greater power of producing heat 

 would be found in fishes in general, than is indicated by 

 the low temperatures of these animals observed by him. 

 When the temperature of the sea was 80°. 5, the tem- 

 perature of the deep seated muscles of the back of the 

 Bonito was found to be as high as 99°, shewing a difference 

 of 18°.5, indicating a very great heat-producing power, if 

 we take into consideration the high conducting power of 

 the medium. This power he attributes to the greater 

 developement of the nerves and ganglia supplying the 

 branchiae in these fishes. When in Malta, he learned 

 from the Tunny fishers, that the blood of those 

 animals, wben stuck, felt as warm as that of a pig. 

 The Tunny and Bonito are allied species, and have 

 the same anatomical development of the nervous system 

 of the Branchiae. This, however, is also to be found 

 in the allied genera of Scomber and Pelamys, which, 

 as far as observation has gone, do not differ in temperature 



