Death and Dissolution of the Organism 361 



In the Zoological Station at Naples in 1906, an 

 actinian, Actinia equina, was alive after having been 

 in captivity fifteen years, and another one, Cerianthus, 

 had been observed for twenty-four years. Korschclt 

 kept earthworms for as long as ten years. The fresh- 

 water mussel may reach the age of sixty years or more 

 and crayfish may live for over twenty years. The 

 differences in the duration of life of mammals are too 

 well known to need discussion. If the cells and tissues 

 are immortal, how does it happen that the duration 

 of life is so characteristic for each species? 



Metchnikoff^ has recently investigated the cause of 

 ''natural" death in the butterfly of the silkworm. The 

 butterfly in this species lacks the organs necessary for 

 taking up food, like the male rotifer or the ephemeridae 

 and hence is already, by this fact, condemned to a 

 short life. Metchnikoff observed that these butterflies 

 could live twenty-three days, but the average duration 

 of life was 15.6 for the males and 16.6 days for the 

 females; and that seventy-five per cent, of them con- 

 tained no parasitic fauna or flora in their intestine. 

 They lose considerably in weight during their lives, 

 but the males still contain the fat body at the time of 

 death. None of the changes accompanying "old age" 

 in man are found in the tissues of these butterflies 

 before death. Aletchnikoff is inclined to believe that 

 the animal is poisoned by some excretion retained in 



^ Metchnikoff, E., Ann. d. Vlnst. Pasteur, 1915, xxix., 477. 



