THE INSURGENCE OF LIFE 151 



lived for at least four years, feeding as well as breathing 

 through its gill-clefts. It is possible that the carp was in 

 part sustained by nutritive material in solution in the 

 water, but there were numerous mayfly larvae, crustaceans, 

 pieces of plants and the hke in the food-canal which must 

 have passed in by the breathing apertures. It may be 

 recalled that according to some speculative anatomists the 

 present-day mouth of backboned animals arose from the 

 fusion of two giU- clefts. 



In any case, though the mouthless carp naturally enough 

 showed no trace of fat, it hved for at least four years, 

 and that is the sort of defiance of handicapping which we 

 wish to illustrate. 



Tenacity of Life 



The toughness of some animals is extraordinary, and is 

 often of considerable practical importance to man, for 

 instance, when he is trying to rid his farm or garden of 

 injurious insects. They are so difficult to kill. The 

 explanation is in part no doubt that the chitinous cuticle 

 is very impervious and resistant, and that larvae in parti- 

 cular are able to close their mouth and breathing-pores. 

 But there is a good deal left to explain. A very careful 

 worker, L. Bordas, notes that he immersed potato cater- 

 pillars {Phtorimoea operculella) in 70 per cent, alcohol for 

 six to eight hours, and found them still able to contract 

 the body, and to move the head and hmbs and jaws ! 



The larva of the cheese-fly, Piophila, can pass right 

 through the alimentary canal of man and dog without being 

 the worse for it, though the canal may be worse for them, as 

 they scratch the deUcate mucous membrane with their 

 oval hooks. Alessandri put some for sixteen hours in 



