16 



THE WEB OF LIFE. 



Prof. W. Lochhead, Macdonald College. 



Perhaps no idea is so full of practical importance to man as the one 

 elaborated by Charles Darwin under the general name of Inter-relations in 

 Nature. By a number of examples Darwin showed clearly that all Nature 

 is a vast system of linkages, one part dependent upon another in an intricate 

 web of life. His most familiar example is perhaps the relation between 

 cats and clover, where clover depends upon bumble bees for the production 

 of seed, and bees are destroyed by field mice and the mice are kept in check 

 by cats. So the story runs: the more cats the fewer field mice, a larger 

 number of bees, a larger crop of clover seed. 



"Web of Life." 



Again, Darwin's masterly work on Earthworms made clear that they 

 are most important agents in maintaining the fertility of the soil and 

 therefore the bread supply of the world. He showed that there often are 

 50,000 (and there may be 500,000) earthworms in an acre (England), that 

 they often pass ten tons of soil per acre per annum through their bodies; 

 and that they often cover the surface at the rate of three inches in fifteen 

 years. 



Since Darwin's time the number of examples of inter-relations has been 

 greatly extended through the observations of thousands of investigators. 

 In our boyhood days we were accustomed to rhyme the chain of events in 

 the House that Jack Built, which ends with "This is the cat that killed 

 the rat that ate the malt that lay in the house that Jack built." In Nature 

 many such chains have been unravelled binding animal with animal and 

 animals with plants and these again with the inorganic world. Man eats 

 the fishes that eat Crustacea that eat infusoria that eat bacteria that feed 

 on decaying organic matter in some pond. 



The metaphor "Web of Life" may be used in two ways. "On the one 

 hand, Nature has a woven pattern which Science seeks to read, each science 

 following the threads of a particular colour. There is a warp and a woof 

 with interlinking and ramifying. We can never tell where a thread will 

 lead to. If one be pulled out many are loosened. 



The "Web of Life" suggests also the web of a spider, often an'intricate 

 system with part delicately bound to part so that the whole system is made 



