72 EX VIRIBUS VIVJMUS. 



differentiation among plants, as having the longest 

 life. The Vertebrata, whith are the highest in evolu- 

 tion of animals, are, as a whole, the longest lived ; 

 for the MoUusca and Crustacea and Echinodermata, 

 though, as stated in the list, they are not known to 

 have a definite limit of life, yet certainly do not, on 

 the whole, exhibit anything like so great a potential 

 longevity as the Vertebrata. Again, amongst the 

 Vertebrata, the longest lived are found in the Mam- 

 malia ; and the whale and the elephant, living re- 

 spectively 300 and 150 years, are the largest, and, in 

 this special characteristic, as highly evolved ^ as any 

 of the class. Then, side by side, we see the whale 

 longer lived than the elephant on account of its 

 greater bulk ; man longer lived than the chimpanzee,^ 

 being larger and more highly differentiated ; the ox 

 longer lived than the sheep and goat ; the lion than 

 the ox, being although not bulkier yet of higher 

 development. So the small Rodents and Insectivora 

 have short lives ; the mouse being said to live a . 

 shorter time than larger allied forms. It would be in- 

 teresting to know as to the longevity of Marsupials ; 

 whether their lower evolution tells strongly on their 



' Mr. Herbert Spencer says, ' Principles of Biology,' vol. ii. p. 479, 

 ' The Elephant (which though otherwise less evolved, is, in extent of 

 integration, more evolved) ' i. e. as compared with man. 



' Mr. Alfred Wallace told the writer that he knew nothing contrary 

 to the supposition that the orang-outang lives as long as the human 

 inhabitants of Borneo. This shews the difficulty there is in observing 

 in regard to the question of longevity. 



