ORGANIC MOVEMENTS 49 



regarded as an independent instinctive phase. Is this 

 stimulus simple or is it individualised, that is to say, 

 specifically combined of elements ? 



It is not very pleasant to be again obliged to leave our 

 question unsolved, but nothing has been done in an exact 

 manner towards answering it. It may seem, of course, as 

 if only typically combined or " individualised " stimuli could 

 suffice to explain the modification of the instinctive acts in 

 exact correspondence with what is required ; but this is 

 only probable, nothing more. 



I once more feel obliged to say that the evidence of the 

 mere fact of regulation among instincts is very scanty at 

 present. Indeed even what we have mentioned about 

 observations of this kind is hardly as well established as it 

 ought to be, and I freely confess that I have treated so- 

 called " facts " here as if they were a little better established 

 than they probably are, simply in order to get a basis for 

 our analytical discussion. It remains, however, a mere 

 discussion of possibilities. For not one of the observations 

 which we have mentioned, regarding the regulability of 

 instincts, has been made with the special purpose of 

 studying that particular point. 



Let us shortly mention the only experimental case in 

 which our problem has been studied with full and careful 

 attention. The entomologist Ch. F. Schroeder, 1 in studying 

 the behaviour of certain caterpillars by the aid of experi- 

 ments, has found that these animals are able to adapt their 

 instinctive acts of spinning most accurately to the real state 

 of the product formed so far ; he not only saw them 

 repairing their weaving, after it had been disturbed inten- 



l. d. zooL Ges. 1903, p. 158. 



4 



