BASIS OF PSYCHICAL-SOCIAL INDIVIDUALITY 615 



female fish does not react against a former mate, but reacts against a new 

 mate, this may merely be due to the loss of a stimulus, owing to former 

 experiences. 



The mechanisms underlying the very complex, strictly determined migrations 

 of eel and salmon over very long distances at definite periods of life, are 

 unknown, but there is no indication that higher psychical processes are in- 

 volved other than those functioning also under other conditions of life. On 

 the whole, the reactions of fishes under given circumstances can be predicted 

 by the student of fish behavior, except in instances in which conditioned 

 reflexes have formed and processes of learning have taken place; in such 

 cases it would be necessary to know certain phases of the history of a fish 

 in order to make the predictability complete. There is no need to assume the 

 existence of free will in the psychical life of fishes. It seems that the greater 

 part of their behavior is determined by rigid simple reflexes and reflex sys- 

 tems, but joined to these are modifiable types of behavior based perhaps on 

 memories of sense impressions and of isolated events, and these may be 

 associated with simple feelings. 



The reactions of birds represent also essentially fixed reflex systems, and, 

 on the whole, they are very similar to those observed in fishes, although the 

 signs used by birds are more complicated, insofar as in addition to various 

 visual stimuli, such as movements, postures, colors, designs, and to olfactory 

 stimuli, finely differentiated auditory stimuli enter into their psychical life. 

 Sounds given off by individuals begin already to play a role among amphibia, 

 but they become much more varied among birds ; there are specific sounds 

 given off by mates and also by parents and children. Among the birds, too, 

 are found species distinctions, sex distinctions, and well developed sex 

 symbolisms used in the sex life of males and females. There is also a seeking 

 for and claiming of territory in which to live and to breed, and the individual 

 which is the first to claim a given territory has the advantage over those that 

 enter later ; the former tends to be the dominant individual. There occur group 

 reactions as well as individual distinctions, and a definite order exists regulat- 

 ing dominance in a group. Furthermore, there are migrations to great dis- 

 tances by birds as well as by fishes, and the flight reflex plays a role in the 

 life of both, as well as in that of animals. 



Again, both fixed inherited mechanisms and a certain degree of modifi- 

 ability of behavior are involved in determining the tendency to complex sea- 

 sonal migrations, which many species of birds exhibit. In some species this 

 process is due merely to definite organ functions and is independent of ex- 

 perience. However, in other birds only some component parts of the reaction 

 system, which leads to seasonal migrations, depend upon fixed reflex systems, 

 while other parts of it appear to be learned from older birds. In the latter 

 case we have to deal with mechanisms which induce a bird to follow other 

 birds in their movements ; in this way conditioned reflexes are set up and 

 the animals learn how to move ; thus a mechanism of tradition may develop. 

 Furthermore, we may find individual differences in the intensity of the 

 tendency to migration, the impulse to migrate being much stronger in some 



