PSYCHIC LIFE OF INSECTS BOUVIER. 459 



joints in the same manner in which the body itself became annulated. 

 Hence the name of Arthropods often given to articulate animals. 



What a difference from the vertebrates. Their skeleton becomes an 

 internal framework. The organism is thus allowed to attain greater 

 dimensions ; the segments are able to fuse to a greater degree and to 

 lose more or less their independence ; all of which results in the re- 

 duction of the number of limbs to only two pairs. 



Now, the relative independence of the segments and the multi- 

 plicity of the appendages have as a corollary the differentiation of 

 these structures, each of which plays a special part in the organism. 

 As Bergson remarks, the various appendages of Articulates are as it 

 were natural implements, which differ from each other in structure 

 as well as in function. Their specialization ma} T be carried so far 

 as to have each part of a single organ perform a separate function. 

 This is clearly seen in the bee, in which the first tarsal joint of the 

 hind legs is transformed into a brush, the tibia into a pollen basket, 

 while the two joints, by the contact of their edges, act as pincers 

 which take up the flakes of wax secreted under the abdomen. It is 

 an admirable instrument wonderfully adapted to the performance 

 of its particular tasks. As a general rule, apart from the changes 

 which they may undergo in the course of specific evolution, the ap- 

 pendages of arthropods are unchangeable in the individual and are 

 narrowly adapted to certain purposes ; they are the tools for instinc- 

 tive work, and in this they differ from the less specialized but more 

 generally useful limbs which serve as implements to the vertebrates, 

 at least to the higher vertebrates. With these latter, as Bergson 

 expresses it, the two pairs of limbs " perform functions much less 

 strictly dependent upon their form," acquiring complete independ- 

 ence in man, " whose hand can do any kind of work." 



It seems, then, that the extraordinary preponderance of instinctive 

 activity among the Articulates has as its essential reason the differen- 

 tiation and the multiplicity of the appendages, in other words, the 

 ehitinization of the integument and the formation of joint lines which 

 results from it. From the beginning these animals were doomed 

 to use organic instruments, and they made the best use possible of 

 these. Their main psychical task consisted in engraving upon their 

 memory and in instinctively repeating the acts to which these organs 

 were adaptable. 



