ii THE WEB OF LIFE 27 



of plants the beginnings of another life. The waves 

 cast up forms of dormant life which have floated from 

 afar, and a terrestrial fauna and flora begin. It is a 

 strange and beautiful story, dead shells of the tenderest 

 beauty on the rugged shoulders of the volcano ; the 

 slowly laid foundation for the reef-building polyps ; at 

 last plants and trees, the hum of insects and the song of 

 birds, over the coral island. 



4. Nutritive Relations. What we may call " nutri- 

 tive chains " connect many forms of life higher animals 

 feeding upon lower through long series, the records of 

 which sound like the story of " The House that Jack 

 built." On land and on the shore these series are usually 



ml 



short, for plants are abundant, and the carnivores feed 

 on the vegetarians. In the open sea, where there is less 

 vegetation, and in the great depths, where there is none, 

 carnivore preys upon carnivore throughout long series 



-fish feeds upon fish, fish upon crustacean, crustacean 

 upon worm, worm on debris. Some fishes, such as 

 mackerel, feed mainly on the minute drifting crustaceans 

 of the open sea (more technically, the Copepods of the 

 Zooplankton) ; these in turn . feed on Infusorians and 

 Diatoms which float in countless numbers in the waters 

 and form the stock of the sea-soup. Many animals that 

 live on the floor of the sea depend on organic debris or 

 detritus, part of which sinks down from the surface, while 

 part is washed down from the shorebeds of sea-grass 

 (Zostera) and seaweeds. This is what is meant by the 

 circulation of matter. 



It follows from these nutritive linkages that disturb- 

 ance or weakness in one link may affect a long chain. 

 Birds of prey and small mammals so-called " vermin ' 



-are killed off in order to preserve the grouse, yet this 

 interference seems in part to defeat itself by making the 

 survival of weak and diseased birds unnaturally easy, 

 and epidemics of grouse-disease on this account the 

 more prevalent. Vanity or gluttony or poverty leads 

 men to slaughter small insect-eating birds, but the 

 punishment falls unluckily on the wrong shoulders- 

 when the insects which the birds would have kept down 



