FACTS AND FACTORS OF DEVELOPMENT 29 



akin to that persistence of the effects of previous experiences in the 

 nervons mechanism which we commonly call memory. It seems probable 

 that this ability of protoplasm in general to preserve for a time the 

 effects of former stimuli is fundamentally of the same nature as the 

 much greater power of nerve cells to preserve such effects for much 

 longer periods and in complex associations, a faculty which is known 

 as associative memory. The embryos, and indeed even the germ cells of 

 higher animals, may safely be assumed to be endowed with protoplasmic 

 and organic memory, out of which, in all probability, develop associative 

 and conscious memory in the mature organism. 



4. Intellect, Reason* — Even the intellect and reason which so 

 strongly characterize man have had a development from relatively simple 

 beginnings. All children come gradually to an age of intelligence and 

 reason. In its simpler forms at least reason may be denned as the power 

 of predicting future events and of reaching conclusions regarding un- 

 experienced phenomena under the influence of past experience. In the 

 absence of individual experience young children have none of this power, 

 but it comes gradually as a result of remembering past experiences and 

 of fitting such experiences into new conditions. Young infants and 

 many lower animals lack the power of reason, though their behavior is 

 frequently of such a sort as to suggest that they are reasoning. Even 

 the lowest animals avoid injurious substances and conditions and find 

 beneficial ones; more complex animals learn to move objects, solve prob- 

 lems, and find their way through labyrinths in the shortest and most 

 economical way; but this apparently intelligent and purposive behavior 

 has been shown to be due to the general elimination of all sorts of use- 

 less activities, and to the persistence of the useful ones. 



The ciliated infusorian, Paramecium, moves by the beating of cilia 

 which are arranged in such a way that they drive the animal forward in 

 a spiral course. However, when it is strongly irritated, the nor- 

 mal forward movement is reversed; the cilia beat forward instead of 

 backward and the animal is driven backward for some distance (Figs. 

 21, 1, 2, 3) ; it then stands nearly still merely rolling over and swerving 

 toward the aboral side and finally it goes ahead again, usually on a new 

 course (Fig. 21, 3, 4, 5, 6). These movements seem to be conditioned 

 rather rigidly by the organization of the animal : they are more or less 

 fixed and mechanical in character though to a certain extent they may be 

 modified by experience or physiological states. Paramecium behaves as 

 it does in virtue of its constitution, just as an egg develops in a particu- 

 lar way because of its particular organization. 



But although limited in its behavior to these relatively simple motor 

 reactions, Paramecium does many things which seem to show intelligence 

 and purpose. It avoids many injurious substances, such as strong salts 

 or acids and it collects in non-injurious or beneficial substances, such as 

 weak acids, masses of bacteria upon which it feeds, etc. It avoids ex- 



