THE WEB OF LIFE 51 



sea-water, partly on the temperature, and partly 

 on the amount of light available. There seems to 

 be no correlation between the surface temperature 

 and the abundance of mackerel, but Dr. Allen has 

 shown a correspondence between sunshine and 

 the catches. Thus we see that, if all flesh is grass, 

 then in the same sense all fish is diatom. 



NUTRITIVE CHAINS IN THE DEEP SEA. If we 

 pass from the sunlit open sea to the floor of the 

 deep sea that strange, dark, cold, silent, plantless 

 world we find carnivorous animal preying upon 

 carnivorous animal through long series fish feeds 

 on fish, fish on crustacean, crustacean on worm, 

 worm on still smaller fry, and all ultimately depend 

 on the basal food-supply the ceaseless shower of 

 moribund atomies sinking from the surface waters 

 many miles, it may be, overhead, like the snow- 

 flakes on a quiet winter day. 



DEPENDENCE OF ONE ORGANISM ON ANOTHER 

 FOR THE CONTINUANCE OF THE SPECIES. Passing 

 from " nutritive chains," we may select a few 

 illustrations of the dependence of one creature 

 upon another for the continuance of its kind. 

 The crowning instances are to be found in the 

 interrelations between plants and animals which 

 secure cross-fertilisation and the distribution of 

 seeds. To both of these Darwin devoted much 

 attention, and they were always favourite subjects 

 with him. 



Every one knows that flowering plants and 

 flower-visiting insects have grown up throughout 

 long ages together, in alternate influence and 

 mutual perfecting. They are now fitted to one 

 another as hand to glove. The insects visit the 

 flowers for food ; in so doing they carry the fer- 



