596 



Cole '96.) The vesicles of Savi appear likewise to belong to the 

 lateral line system. 



Although there are still some discrepancies and omissions in our 

 accounts of the distribution of the cranial nerves, I think it may be 

 stated that all sensory structures of ectodermal origin 

 are supplied by components of the Vth. (including 

 spinal Vth. components running in other nerves), 

 Vlllth., and lateral line nerves, and that all fibres 

 supplying such structures have their central endings 

 in the Nucleus funiculi, the tuberculum acusticum, 

 or the cerebellum, except such as pass through the acusticum as 

 arcuate fibres. On the other hand, all sensory structures 

 of entodermal origin are supplied by Vllth., IXth., and 

 Xth. components, and all fibres supplying such struc- 

 tures find their central endings in the Lobus vagi. 

 I leave out of consideration sensory fibres to mesodermal structures 

 ("muscle sense", &c.), of which we know nothing in fishes. Strong ('95) 

 has emphasized the fact that the fibres entering the Fasciculus com- 

 munis in Amphibia (= L. vagi in fishes) are mostly splanchnic fibres, 

 innervating the alimentary canal and its appendages. Kingsbury's ('97) 

 analysis of the sensory centers agrees in the main with my own, but 

 he separates the spinal Vth. and the cerebellum from the acusticum 

 more than seems to me warrantable. The generalization that the 

 ectodermal and entodermal sensory systems are quite distinct has not 

 before been expressed, I believe. 



I have sufficiently emphasized the isolation of the Lobus vagi 

 from the centers for the nerves of integumentary sensation. The 

 question of the homology of the centers for the two sets of nerves is 

 a difficult one. The Nucleus funiculi, acusticum, and cerebellum would 

 seem to be directly homologous with the dorsal horns of the cord, 

 and the nerves entering them with the dorsal roots of the spinal 

 nerves. The structure of the centers is similar, and the Vth. and 

 lateral line nerves, and perhaps also the Vlllth., send fibres to end 

 in all three centers. If this is the correct interpretation, then there 

 is probably no structure in the cord with which the Lobus 

 vagi can be considered homologous. This lobe lies wholly 

 dorsal and mesial to the centers for ectodermal sensation, and at the 

 posterior end of the medulla it lies very close to, or actually in, the 

 dorsal raphe. I do not know any structure in the cord in the adult 

 which corresponds to it. It is to be noted further, that there is in 

 the trunk region no demand for such a center. The nerves which 



