LIASSIC PTERODACTYLES. 495 



Pterosaurs have been found associated witli their tendons,^ that detached caudal vertebrae 

 of ArchcEopteryx might he recognised through the want of them. 



We may confidently concluile that the Oolitic mud which has entombed the greatest 

 number and variety of the flying reptiles of its period would have shown us, when petrified 

 into lithographic slate, their feathers, if, as warm-blooded animals, they had needed such 

 heat-conserving a covering. The plumose clothing of the long-tailed bird of the period 

 proves its hsematothei-mal character, as the want of it shows the long-tailed pterosaur to 

 have been cold-blooded. 



The tyro, fresh from the lecture-room of his physiological teacher, ambitious of soaring 

 into higher regions of biology than were opened to him at the medical school, impressed 

 with the relations of active locomotion to generation of animal heat, may be pardoned for 

 inferring that the amount of work involved in sustaining a Pterodactyle in the air would 

 make it, physiologically, highly probable that it was a hot-blooded animal. But a competent 

 friend, finding him bent on rushing with such show of knowledge into print, would counsel 

 him to provide himself with a thermometer adapted to the delicate testing of the internal 

 heat of small animals. So provided, if he should chance to beat down a cliafer in full flight, 

 the experiment, made with due care and defence of the fingers guiding the instrument, 

 would teach him how fallacious would be the inference that, because an animal can fly, it 

 must, therefore, be hot-blooded. Unless he happen, in introducing the bulb by the 

 widened vent into the abdomen, to plunge it into a mass of ova, he will find the heat of 

 the beetle, notwithstanding the amount of work involved in sustaining and propelling 

 itself in air, not to exceed by more than one degree that of the atmosphere. If he has 

 knocked down a female cockchafer prior to oviposition, the ovarian masses may indicate half 

 a degree, or even one degree, higher of temperature (Fahr.). With the cooling of the air 

 in the summer lu'ght the tem[)erature of the Melolontha concurrently falls. So, likewise, 

 would that of the flying reptile, whatever " amount of oxidation and evolution of waste 

 products in the form of carbonic acid " "" might have attended their exercise of flight. The 

 constant correlative structure with hot-bloodedness is a non-conducting covering of the 

 body. We may with certainty infer that ArchcBopterijx was hot-blooded, because it had 

 feathers, not because it could fly. 



There is no ground, from observation of the Sharks and Porpoises that accompany 

 swift-sailing vessels, maintaining themselves near the surface, exercising their several and 

 characteristic evolutions in quest or capture of prey, for inferring that tlie amount or the 

 energy of muscular action is very different in the two surface-swimmers. 



Sharks have and, no doubt, work a greater proportion of muscle than Cetaceans; a 

 less proportion of their body is excavated into visceral cavities. Yet the Shark is cold- 

 blooded ; its temperature rises and falls with that of its medium ; it has no provision, by 



1 As seen in PI. 1 6, at cd. 



2 'Proceedings of tlie Zoological Society,' April, 1867, p. 417, Prof. Huxley " On the Classificatiou 

 of Birds." 



2^ 



