41 

 communis in amphibians; and by Herriok ('99) for the bony fish, 

 I concUne that this tract is developed in Niustelus to a con- 

 spicuously less degree. The sit'nificance of this smaller siee 

 for the brain of the selachian is not clear. The communis 

 fibres are essentially viscero-sensory , but there have been 

 annexed to the systeni certain external sense-organs, such as 

 taste-buds and end-buds. There are no observations indicating 

 marked differences between the visceral connections of this 

 system in >/,ustelus as compared with teleosts and amphibians. 

 In fact, the archaic value and deep-seated physiological impor- 

 tance of such connections in all vertebrates would lead us to 

 infer a considerable similarity in related groups. We thus 

 appear to be thro.vn upon the more recent additions to the sys- 

 tem for the explanation. It seems to me that a comparative 

 investigation of end-buds and taste-buds will contribute much 

 toward the solution of questions pertaining to their central 

 tracts. 



-5. The V iscero-Votof Kucleus. 

 The adoption in this paper of the name viscero-motor nu- 

 cleus expresses the need for a general term which shall includ( 

 all members of the morphologically continuous colunn of cells 

 giving origin to the motor fibres of the V, VI], IX, and X 

 nerves. This nucleus is the continuation into the oblongata 

 of the paracentral nucleus of Onuf and Collins ('9B), and the 



