THE EVIDENCE OF THE CENTRAL NERVOUS SYSTEM 6 J 



compelled to pass the whole of his food through the narrow oesophageal tube, 

 still existent in him as the infundibular tube. This, then, is the working 

 hypothesis upon which this book is written. If this view is right, that the 

 Vertebrate was formed from the Palajostracan without any reversal of surfaces, 

 but by the amalgamation of the central nervous system and alimentary canal, 

 then it follows that we have various fixed points of comparison in the central 

 nervous systems of the two groups of animals from which to search for further 

 clues. It further follows that from such starting-point every organ of importance 

 in the body of the arthropod ought to be visible in the corresponding position in 

 the vertebrate, either as a functional or rudimentary organ. The subsequent 

 chapters will deal with this detailed comparison of org*ans in the arthropod and 

 vertebrate respectively. 



