10 PJUJCEKDIXCiS OF THE 



siiine position in the brain as the cesophaj^us in the Invertebrate 

 group. Supra-infundibular nerve-mass was then tlie same as the 

 supra-oesophageal, infra-infundibular as infra-oesophaKeal, and it 

 was seen that the function corresponded marvellously- So 

 powerful was the fetish of the inviolability of the aliinentary 

 canal, tliat no one of these observers ever noticed that if the 

 infuiidibuluin is the old oesojthagus, it leads directiv into the great 

 cavity of the ventricles of the brain, which again lead into the 

 straight narrow caual of the spinal cord and so through the 

 )ieurentoric canal to the anus; that in fact if the infundibulum is 

 the (esophagus, the rest of the liuiiig-walls of the cavitv of the 

 central nervous system corresponds «ord for word with the rest 

 of the Iinvrtebrate alimentary canal. On the contrary, they 

 considered the homology could only hold good by turning the 

 animal topsy-turvy and making the back of the Invertebrate 

 correspond to the ventral surface of the Vertebrate. Such a 

 method was doomed to failure and is now universally discredited. 

 As to the alternative hypothesis of an origin from some non- 

 segmented Invertebrate, please think what it implies and consider 

 seriously whether it is possible to accept it. I imagine we may 

 take it lor granted that we know the nature of all the main group's 

 of animals alive on the earth at the present time, and as far as 

 1 know the geological record has not brought to light any foi-ms 

 which are not capable of being classified either among or in con- 

 nection with our present main groups; yet the assumption of this 

 hypothesis is that from some unsegmented animal low down in 

 the scale a group of segmented animals has arisen, in which the 

 alimentary canal was always ventral to the central nervous system 

 and that this group gave origin to the Vertebrate. The absence of 

 any evidence of such chain among living animals at all comparable 

 to the well-marked evidence in the case of the Appendiculata, 

 makes this hypothesis an improbable one ; and when the hypo- 

 thesis further necessitates that not only the central nervous system 

 of such segmented animals has been built up on exactly the 

 same lines as the central nervous system of the Appendiculata, 

 hut, contrary to all other nervous systems, has been formed hollow, 

 and that that hollow tube has been formed in such a shape 

 and in such a position with respect to the true nervous elements 

 as exactly to mimic the alimentary caual of the Appendiculata 

 with respect to its central nervous system, — I ask you plainlv, 

 does not the improbability amount to an absurdity? This I 

 claim to be the great characteristic of the Vertebrate which 

 differentiates it from all other animals — the presence and nature 

 of this tube around which the central nervous system is grouped : 

 and I beg that those speakers who follow after me and disagree 

 with my conclusions, will give some explanation of the presence 

 and peculiarities of this tube. To me and to all my friends who 

 are accustomed to deal with the Vertebrate central nervous system, 

 the explanation I have given is so self-evident and natural, that it 

 is impossible tc look at the matter in anv other wav. 



