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THE AMERICAN NATURALIST [Vol. XLI 



ment was the best standard of size to take — better than length, 

 for instance. As a matter of fact, the fish were very much the 

 same length; the Exocoetus being rather the longer. 



"The drawings, I think, explain themselves. The flying-fish 

 muscles were, as you see, considerably larger, both in area and in 

 thickness, than in Hemiramphus, and the same w^as the case with 

 the muscles on the deep surface of the fin. In their arrangement 

 they were much the same in both fish and the same as in other 

 bony fishes (the cod, for instance). The numbers on the surface 

 of the fins are the points where I took the thickness of the muscles 

 by plunging a needle into it and measuring the depth to which the 

 needle entered. You will notice the great length of the muscles 

 in Exocoetus: a long muscle means a proportionate length of con- 

 traction. 



" . . . . there is a very marked difference in the size of the muscles 

 of these two fishes .... 



" Believe me, yours faithfully, 



R. H. BURNE 



(Assistant in Museum). 



The above tracing seems to give, roughly, about 44 times greater 

 bulk of muscle to the Exocoetus than to the Hemiramphus. With 

 this light it will not be out of place to requote and amplify the one 

 "proof," distinguishing the addition by itahcs: — "The pectoral 

 muscles of birds depressing their wings weigh on an average one 

 sixth the total weight of their body, the pectoral muscles of bats one 



thirteenth, the muscles of the pectoral fins of flying-fish one 



thirty-second," and the mutcles of a nearhj related non-flying fish 

 only one hundred and fifty-fourth. 



As before, it does not prove that bats or flying-fish flap or do 

 not flap their wings, but it gives a different and, I hope, a proper 

 aspect to the figures which have done duty — of a kind — for so 

 many years. 



