86 SECRETS OF ANIMAL LIFE 



therefore flourish so abundantly that the supply of 

 available nitrogenous food for the Phyto-plankton 

 is greatly lessened. According to Sir John Murray 

 and Professor Jacques Loeb, the reason is rather 

 that low temperature slows the vital processes and 

 increases the length of life, so that several gener- 

 ations of Plankton organisms are living at the same 

 time in the colder waters. It is probable that both 

 views are correct. 



It is hardly necessary to say that the analogy of 

 producers, consumers, and middlemen should not 

 be pressed too hard. Thus it is quite useful to 

 follow a recent investigator, Dr. Blegvad, in regard- 

 ing the detritus-eating animals as producers in 

 relation to the carnivores, just as fishes are pro- 

 ducers in relation to the supreme carnivore Man. 

 Bivalves and other animals which feed at a low 

 level on minute debris are making available to any 

 creature that can eat them supplies of energy which 

 would otherwise be wasted| Plaice in the Kattegat 

 are very fond of lancelets, which subsist on detritus 

 particles; so that in respect to the plaice the 

 lancelet is a producer or a middleman. The main 

 idea is that of the circulation of matter, or of what 

 Sir John Murray, who did so much to make Oceano- 

 graphy a science, called " the never-ending cycle." 

 The Algse find nourishment mingled with the water 

 that bathes them, and, using chlorophyll to " con- 

 jure with the sunbeams," they build up organic 

 compounds from inorganic constituents. Vegetable 

 proteins are thus formed, and when these are eaten 



