312 The Unity of the Organism 



thick, chitinous secretion from the whole outer surface of the 

 hjpodermis. Here, too, we have an activity which, though 

 manifested in a very different way, is even more clearly one 

 of growth and development. And when the workers of 

 (Ecophylla or Polyrhachis use their larvae for weaving the 

 silken envelope of the nest, as described in Chapter XIII, 

 we have a further extension and modification of the cocoon- 

 spinning activities. In this case the spinning powers of the 

 larva are utilized for the purpose of producing an envelope, 

 not for its individual self, but for the whole colony. In 

 conventional works this latter activity would be assigned a 

 prominent place as a typical instinct, the spinning of the 

 cocoon might also be included under this head, but the form- 

 ation of the puparium, or pupal skin, would be excluded 

 as a purely physiological or developmental process, yet this 

 last, no less than the two other cases, has all the fundamental 

 characteristics of an instinct."^ 



Then immediately follows this statement, especially signi- 

 ficant for the proposition of our hypothesis which assigns to 

 the individual organism the chemical value of an elementary 

 substance: "Viewed in this light there is nothing surprising 

 about the complexity and relative fixity of an instinct, for it 

 is inseparably correlated with the structural organization, 

 and in this we have long been familiar, both with the de- 

 pendence of the complexity and fixity of parts on heredity 

 and the modifiability of these parts during the life-cycle 

 of the individual. Fixed or instinctive behavior has its 

 counterpart in inherited morphological structure as does 

 modifiable, or plastic, behavior in well-known ontogenetic 

 and functional changes." 



The statement that surprise is largely taken away from 

 such elaborate manifestations of instinct as those here de- 

 picted, by recognizing that the instincts are "inseparably 

 correlated with structural organization" and have their 

 "counterpart in inherited morphological structure," will, no 



