AN ESSA Y ON LONGEVITY. 13 



carnivora, most birds, reptiles, fishes, and aquatic 

 animals, that any suppositions as to their duration of 

 life can rest on but few facts. In reply to enquiries, 

 Mr. Charles Darwin writes that he has no informa- 

 tion with regard to the longevity of the nearest 

 wild representatives of our domesticated animals, 

 nor notes as to the longevity of our quadrupeds.^ 

 Mr. Thomas Bell, the author of most valuable works 

 on ' British Quadrupeds,' ' British Reptiles,' and ' Bri- 

 tish Crustacea Podophthalmia,' in reply to special 

 enquiry, writes that the opportunities of observation 

 are few, and the results necessarily uncertain as to 

 length of life in Reptiles and Crustacea.^ Dr. Gun- 

 ther, of the British Museum, a most able ichthyologist 

 and naturalist, remarks, in a letter in reply to en- 

 quiries, — 'There is scarcely anything positive known 

 of the age and causes of death of various fishes.' So, 

 too, in Mr. Yarrell's works little is said of duration 

 of life; whilst in Mr. Gwyn Jeffreys' admirable treatise 

 on the British Mollusca a similar absence of know- 

 ledge with regard to those animals is admitted. The 

 Insects form a remarkable exception, since in a great 

 number of them the duration of life is well known.^ 



' Mr. Darwin very kindly furnished me with a note relative to the 

 age of certain birds, which is quoted in the Table of Statements, which 

 follows. 



'^ He, however, gives two facts which are mentioned in the Table of 

 Statements. 



' Only comparatively ' well known,' however, for the relative duration 

 of life in different species of insects, involving a matter of months and 

 days, is not known. 



