Natural Histm'y of the Shark. 361 



elude that the Sajmniis spinostis is a Ground Shark ; and Dr. 

 Andrew Smith says of the specimens occasionally found at the 

 Cape of Good Hope, that they are described by the fishermen as 

 sluggish and unwieldy in their movements, — seldom observed on 

 the surface, and hooked always when they are fishing in deep 

 water, and when the bait is near the bottom. As the spinosus 

 resembles in this respect the Scyllium or true Ground Shark, 

 Dr. Smith concludes, that if we regard only its internal organiza- 

 tion, we should be disposed to consider it as closely allied to 

 that genus*. The Scyllium we have already spoken of as ovi- 

 parous. 



Of the Sharks that frequent the surface waters, the Blue Shark 

 {Carcharias glaucus), the White Shark (C vulgaris), and the 

 Basking Shark {Selachus maximus) are the most conspicuous. 

 They are all three of gigantic size, but two only are voi-acious, 

 if the word 'voracity' be restricted to a predacious appetency 

 for large animals. Of the ZygceruB or Hammer-headed Sharks, 

 which are said to possess habits very similar to those of the 

 other large Squalidts, sharing with them their characteristic 

 rapacity, and not hesitating to attack man when an opportunity 

 ofi'ers, we have not such specific facts respecting their mode of 

 utero-gestation as to say whether their oeconomy is so absolutely 

 viviparous as to i-ender a resort to the increased temperature of 

 the surface waters necessary for maturing the foetus ; they are 

 not very frequently seen in the broad ocean. That which the 

 atmosphere does for the eggs of the Ground Sharks, anchored as 

 we have described, by their tangled tendrils in shoal waters, the 

 viviparous Sharks must effect by constantly haunting such depths 

 only as are heated by the daily sun. 



Now, as we know that the lower the animal is in the scale of 

 organization, the nearer it approaches to the plant in compara- 

 tive feebleness of function in generating heat ; and as we know 

 that the heat of worms, insects, Crustacea and mollusca, and of 

 fishes and amphibia, is commonly only two or three degrees 

 above that of the medium in which they are immersed, and that, 

 absolutely colder in their circulatory fluids than the higher ani- 

 mals, they are incapable of resisting any considerable changes 

 in the surrounding medium, whether it be from heat to cold or 

 from cold to heat; we necessarily know also that their blood 

 must be absolutely gelid in the polar regions, and cold in the 

 temperate zone in the cold months of the year, and they must 

 be heated to a degree of warmth equal to that of the medium 

 in which they move in the hot season, whether that medium be 

 air or water. 



* Dr. Andiew Smith, on the Zoology of South Africa, No. 1. 



