45 



are, I think, persistent organs whose higher psychical function has 

 been lost, like that of the labial vibrissae, though they probably have 

 a warning function in a few species. 



The apparently insignificant hairs on the head and first two seg- Thoracic hairs. 

 ments have really far more claim on our attention than the anal setae. 

 STANLEY* in his work on the Emotions, postulates undifferentiated pain 

 as the primitive and simplest form of consciousness, and I think that 

 we may take it as a general rule that sensory hairs, which do not 

 suggest by their position and structure any highly differentiated sense, 

 have this function, and not as is generally assumed by physiologists the 

 neutral sense of tact or touch. 



If the feeling tone produced by stimulation of these hairs was 

 painful it would generate the following habit. When any object touched 

 the head or anterior segments the larva would shrink away and retire 

 down its tube ; but when safe within its tube it would be liable to 

 knock the hairs against the sides and consequently as soon as the 

 danger was over it would come out a little way again. Thus would 

 gradually be evolved the habit of resting with at least the head exposed. 

 This is to some extent the case with C. pnsio and more so with the 

 stalk-cased larva, which has indeed scarcely room for its whole body 

 within its tube as this is very short. It is to be noticed that the hairs 

 of this larva are larger and more numerous than those of C. pusio. 



We shall find more convincing evidence among larvae such as 

 Culex (Gnat), Anopheles (Mosquito) and Corethra. In these larvae we 

 find large single or multiple hairs projecting from all parts of the body 

 and in many instances nerve connections can be traced, and the habit 

 that we find common to these and other like aquatic insects is 

 that they all avoid contact with solid objects. This avoidance of objects 

 leads to the habit of living in the open water rather than among 

 weeds. Simple tactual sense scarcely seems likely to cause this habit, 

 while a disagreeable feeling-tone, a kind of undifferentiated pain, might 

 produce it. On the other hand Ceratopogon, Tanypus and many of the 

 smaller Chironomus-larvae, or " Motitators " as MEINERT called them, 

 whose bodies are quite free from long hairs, are found creeping and 

 swimming about among water-plants. 



* Evolutionary Psychology of the Emotions, ch. II. 



