THE ORGANIC AND THE INORGANIC 293 



manifested by a dog or by much that we see in the 

 behaviour of ants. No rigid distinctions between 

 tropisms, such as we have mentioned above, and the 

 reflexes that may be taken to constitute instinctive 

 behaviour, can be established. Minute analysis, such 

 as that carried out by Jennings on the swimming 

 movements of the Protozoa, leaves us quite in doubt 

 as to how these modes of behaviour are most properly 

 to be described ; and all the controversy as to the 

 nature of tropisms, reflexes, instinct, and intelligence 

 surely indicates that these modes of behaviour have 

 something that is common to all of them, and that no 

 clear and certain distinction can be said to separate 

 one from the other. Even those psychic processes 

 which we call intellectual do not seem to be different 

 in kind from some that we attribute to the lower 

 animals : the Protozoan Paramcecium studied by 

 Jennings, or the crabs, crayfishes, and starfishes studied 

 by Yerkes and others really learn to perform actions, 

 but this learning is said to be the result of a process 

 of " trial and error." The animal tries one series of 

 movements and finds that it fails, tries another and 

 another with a similar result, and in the end finds one 

 that is effective. This is remembered, and when the 

 same problem again confronts the animal it is solved 

 after fewer trials, and finally, after experience, the 

 end-result is attained at once without previous trials. 

 Now many of what we call truly intellectual pro- 

 cesses are certainly processes of precisely this nature. 

 Hypothesis after hypothesis occurs to the scientific 

 man (or to the detective, or to the engineer confronted 

 with some exceptional difficulty) , and one after another 

 is tested by actual trial, or by a process of reasoning 

 (which is really the rapid and formal resuming of 

 previous experience), until a hypothesis verifiable, or 



