lo ANIMAL AGGREGATIONS 



That social instinct may be acting in given cases is not to be denied, 

 but there has been an increasing and wholesome tendency to depre- 

 cate the use of this term to cover ignorance. 



"Instinct" is hard to define. The most satisfactory definition 

 known to the writer is that of Wheeler, who says (1913a): "An in- 

 stinct is a more or less complicated activity of an organism which is 

 acting (i) as a whole rather than as a part; (2) as a representative of 

 a species rather than as an individual; (3) without previous experi- 

 ence;' and (4) with an end or purpose of which it has no knowledge." 



It is obvious to one who has observed the reactions of animals 

 that there are two types of behavior: the learned and the unlearned. 

 Much of the latter is frequently called "instinctive," with propriety, 

 though in the case of many highly organized animals, including man, 

 there has been an unfortunate tendency to regard, as instinctive or 

 unlearned, behavior that is in reality based on very early training 

 which has been entirely forgotten or overlooked. 



In man breathing, swallowing, gland secretion, and muscle con- 

 traction are all unlearned; and some of these, for example the secre- 

 tion of certain glands, cannot be effected by learning. These un- 

 learned reflex actions of parts of organisms seem to be the simplest of 

 a series of unlearned responses whose other categories are those re- 

 flexes of an entire organism commonly called "tropisms," and the 

 more complex behavior usually called "instinctive." 



It is becoming increasingly difficult to draw hard and fast lines 

 between instincts and tropisms, or between either of these and the 

 general functioning of Hving cells. It is further impossible to dis- 

 sociate any of these three categories of behavior from the activities 

 concerned with growth and development. If one considers in this 

 connection the metamorphosis of a larva into an adult, which is 

 usually regarded as the function of growth and development, one 

 finds the processes concerned so inextricably bound with major and 

 minor activities of the animal that the instinctive behavior cannot 

 be clearly separated from the other processes going on at this time. 

 Is the production of the silk cocoon of the moth an instinctive action, 

 while the production of the thickened hypodermis to form the chrys- 



' Or without modification caused by experience (W. C. A.). 



