AN ESSAY ON LONGEVITY. 73 



longevity, or whether bulk affects it most. The large 

 Kangaroo, were longevity, regulated by bulk alone, 

 should live longer than the sheep. The Reptiles 

 present inter se the same relations ; the crocodiles 

 and chelonia, which are certainly those of greatest 

 individuation, being longest lived. So too the Fishes, 

 as far as facts go, the Pike being a highly evolved 

 fish. The Sharks may be guessed from their great 

 size to have very long lives, which confirms the rule 

 as to high development, though of course it cannot 

 as to bulk. That bulk and development increase 

 together is well ascertained from general principles. 

 The Sharks of the later Tertiary period are calculated 

 from the size of their teeth to have measured between 

 eighty and ninety feet in length, and may have had 

 a proportionate longevity. Speculation might lead 

 one to attribute enormous longevity to the gigantic 

 extinct mesozoic Reptiles. Amongst MoUusca, the 

 highest in evolution are the highest in longevity, 

 if we may judge by the size and rate of growth 

 6f some Cephalopods, both recent and extinct, as 

 compared with Conchifers and Brachiopods. The 

 Insects inter se present facts supporting the truth of 

 the proposition as to high evolution : the Coleoptera 

 and Orthoptera, undoubtedly from their carnivorous 

 habits (in many cases) and generally dominant 

 character, the most highly evolved, are the longest 

 lived, according to observation, e. g. Scarabffius and 

 Mantis. 



