MOTOR NUCLEI IN. PHYLOGENY A471 
The motor roots of the spino-ocecipital nerves course obliquely 
cephalad and mesiad to reach their nuclei of origin in the ter- 
minal rostral portion of anterior horn of the cord (fig. 1). There 
is no indication whatever of any separation between these nuclei 
and those of the succeeding ventral spinal nerves. 
Nu. F.c. 
R.sp.occ.s .,. 
R sp.oce.m.(1) 
Fib.arc.int. 
Fib.arc.int. 
Figs. 1 to3 Bdellostoma dombeyi. Outlines of transverse sections to illus- 
trate the topography of the medulla. Sensory areas and fiber tracts indicated 
diagrammatically. Figures 1 to 6 drawn to same scale. Abbreviations: Ar.g.c., 
general cutaneous area; F’.c., fasciculus communis; Fib.arc.int., fibrae arcuatae 
internae; Laq., laqueus; s. tractus tecto-bulbaris et spinalis; Nuw.f.c., nucleus 
and region of fasciculus communis; Nuw.sp.occ.m., rostral portion of anterior 
horn (spino-occipital motor nucleus); Nw.VII.m., caudal end of nucleus motorius 
N. facialis; Nu.X.m., nucleus motorius N. vagi; R.sp.occ.m.(1)., first motor 
rootlet of first spino-occipital nerve; R.sp.occ.s., part of sensory root of first spino- 
occipital nerve; R.X.m.(2)., second motor rootlet of vagus; R.X.m.(5)., fifth 
motor root of vagus: 7'r.cb.sp., tractus cerebello-spinalis. 
