110 THE BRAIN OF INVERTEBRATES. 



either direct to the posterior part of the Brain or to its 

 peduncles. They thus contribute internal impressions 

 which impinge upon the Brain side by side with those 

 coming through external sense organs. 



12. This Visceral System of Nerves in invertebrate ani- 

 mals has, when compared with the rest of the Nervous 

 System, a greater proportional development than among 

 vertebrate animals. Its importance among the former is 

 not dwarfed, in fact, by that enormous development of the 

 Brain and Spinal Cord which gradually declares itself in 

 the latter. 



13. Thus impressions emanating from the Viscera and 

 stimulating the organism to movements of various kinds, 

 whether in pursuit of food or of a mate, would seem to 

 have a proportionally greater importance as constituting 

 part of the ordinary mental life of Invertebrate Animals. 

 The combination of such impressions with the sense- 

 guided movements by which they are followed, in complex 

 groups, will be found to afford a basis for the development 

 of many of the Instinctive Acts which animals so fre- 

 quently display. 



