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men. The author endeavours to extend this analogy to other species 

 of the same family, which, according to the reports of the fishermen 

 of whom he made inquiries, have a high temperature, and in whose 

 internal structure he noticed similar peculiarities as in the Thunny ; 

 namely, very large branchial nerves, furnished with ganglia of consi- 

 derable size. In this respect he considers that in these fishes the 

 branchial system of organs makes an approximation to the respiratory 

 apparatus of the Mammalia, and that it probably contributes to the 

 elevation of temperature, resulting from the more energetic respira- 

 tion which he supposes to be exercised by these organs. He, how- 

 ever, thinks it not improbable that these fish may possess means of 

 generating heat peculiar to themselves, and of which at present we 

 have no adequate idea. He conceives that the situation of the kid- 

 neys, of which a considerable portion is even higher than the stomach, 

 and posterior to the gills, and which are of large size, and well sup- 

 plied with nerves and blood-vessels, may possibly act a part in the 

 production of an elevated temperature ; but, on the whole, he is dis- 

 posed to ascribe the greatest share of this effect to the superior mag- 

 nitude of the branchial nerves. 



