COXCLUSTOX. 191 



to the lower animals we do not know what pecu- 

 liarities of the brain of an ant make it the re- 

 cipient of a higher instinct, or give its possessor 

 greater capacities for dealing with new and unex- 

 pected difficulties than are possessed by most other 

 insects, and if any reader has a marine aquarium, 

 and will make a few experiments in taming prawns, 

 and watching their proceedings, he will discover 

 symptoms of intelligence beyond Avhat the structure 

 of the creature would have led him to expect. 



Animals usually possess some one leading charac- 

 teristic to which their general structure is subor- 

 dinated. Man stands alone in having the whole of 

 his organization conformed to the demands of a 

 thinking, ruling brain. To pass at once to the 

 other extreme, we observe in the infusoria a restless 

 locomotion, probably subservient to respiration, but 

 utterly inconsistent with a well-developed life of 

 relation, or with manifestations of thought. Indi- 

 vidually, therefore, the life of an animalcule may 

 be summed up as a brief and restricted, but 

 vigorous organic energy, and if the amount of 

 change which a single creature can make in the 

 external world, is inconceivably small, the labours 

 of the entire race alter the conditions of a prodigi- 

 ous amount of matter. Microscopic vegetable life 

 is an important agent in purifying water from the 

 taint of decomposing organisms. By evolving oxygen 



