614 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



with attributes of graded superiority or inferiority, these gradations serve 

 to distinguish individuals. Females learn to recognize their former mates; 

 they attack strange males of the same species, but do not react against their 

 old mates. Parent fish learn to recognize their young. There are very distinct 

 and fixed behavior patterns relating to the sexual life, preceding the mating 

 act; also, the spawning and brooding functions are rigid, inherited species 

 characteristics. Movements which have the effect of suggestions and lead 

 to imitations of movements play a part in these actions. In the selection of 

 territories and nest sites, color distinctions are involved ; but here, also, previ- 

 ous experiences of having lived in an environment with certain colors may 

 influence the choice of the nesting place. 



The signs which serve as symbols determining recognition, schooling, sexual 

 acceptance or attack in the social life of fishes, are partly visual, such as recog- 

 nition of movements and fine distinctions in color designs; but also olfactory 

 stimuli, extracts of skin, wounds, substances extracted from dead fish of the 

 same species call forth avoidance reactions in Phoxinus. The essential be- 

 havior patterns are genetically determined species characters ; but learning 

 leads to certain modifications in the behavior patterns. If a certain individual 

 is differentiated from other individuals belonging to the same species, this 

 does not necessarily mean that the individual recognition in fishes has the 

 same significance as in man ; although the same term is used in both instances, 

 we have probably to deal with processes of a different nature. In fishes the 

 recognition of an individual signifies the sorting out of a fish as representing 

 a child, a former mate, or a certain degree in the dominance series, one fish 

 being differentiated from others probably by means of a single sign, such as 

 a color pattern of the head, a particular movement, or perhaps a certain 

 olfactory stimulus given off by this fish. In man, on the other hand, an 

 individual represents a composite of many different bodily signs and psychical 

 expressions, which have acted on another individual by certain movements, 

 have given rise to certain experiences and have aroused hopes or fears. 

 However, the most primitive and the highest vertebrates — fishes and man 

 — give evidence, in common, that the distinction of individuals and species 

 depends directly on characteristics of organs and their functions, on move- 

 ments and expressions, and not on the organismal differentials. These organs 

 differ in structure and function in different species and individuals, and the 

 behavior patterns differ accordingly ; but both the structure and functions of 

 organs and behavior patterns are connected and correlated with the organismal 

 differentials. 



In addition to the reaction modes which we have mentioned, there are some 

 further indications of the ability of the fish to modify the rigid behavior 

 patterns as the result of experience. Frustration or perhaps painful sensations 

 result in an avoidance of certain motor activities, which would have been 

 carried out under normal favorable conditions. But there is no suggestion 

 that reproductions of sensations or events are the essential factors in these 

 learning processes or are the necessary cause of modifications in the way 

 of reaction, although such reproductions may perhaps also participate. If a 



