MOTOR NUCLEI IN PHYLOGENY 475 
sections of the brain stem taken at various representative levels 
in the series, where these relations can be accurately recorded. 
4. For the sake of convenience the general outlines and 
shapes of the nuclei are depicted quite diagrammatically. In 
Nu.V.mag.m. 
Figs. 4 to 6 Bdellostoma dombeyi. Outlines of transverse sections to illus- 
trate the topography of the medulla. Sensory areas and fiber tracts indicated 
diagrammatically. Abbreviations: Nuw.ac., nucleus acusticus; Nu.V.mag., 
nucleus motorius N. trigemini (magnocellularis); Nu.V.paf., nucleus motorius 
N. trigemini (parvicellularis); R.V.m., radix motorius N. trigemini; R.VII.m., 
radix motorious N. facialis; VJIJ., acoustic fibers. Other abbreviations as in 
figures 1 to 3. 
