The brain of Acipenser. 251 
Explanation of the Text-figures. 
Fig. A. Transverse section of medulla through the lower olive. 
Fig. B. Frontal sections through the dorsal part of the cord in 
the region of the cervical bundle. The section represented in A passes 
through the caudal part of the commissura infima Halleri (com. inf. H), 
that represented in E is about 3 mm farther caudad. Both median 
and lateral bundles disappear about 3'/, mm caudal to the commissure. 
c.b cervical bundle; c.b.l lateral bundles; ç.b.m median bundle; c.c 
canalis centralis; f.d funiculus dorsalis; r.s reticular substance sur- 
rounding the cavity; s.g substantia gelatinosa of the dorsal horn. 
Fig. ©. Lobus vagi. Short neurite of a cell whose body lies in 
an adjacent section. The curved line represents the inner surface of 
the lobe. Frontal section. 
Fig. D. Section inclined forward at an angle of about 45 degrees, 
passing through the ventral root of the VII nerve (VII.v), the dorsal 
root of the V (V.d), the secondary vagus nucleus (sec.v.n) and its 
commissures (sec.v.coms), and the tectum. The most anterior of the 
four secondary vagus commissures is small and lies dorsal to the 
others; cer body of cerebellum; com.tr.l-c commissure of the tractus 
lobo-cerebellaris. 
Fig. E. Horizontal section through the cerebellum and tectum, 
showing the tractus tecto-cerebellaris I and Il. cer body, J.] lateral 
lobe, valv valvula of cerebellum; fecé tectum opticum; y bundle y 
from base of mid brain to valvula; IV.n the fourth nerve. Two 
cells with short neurites are shown. 
Fig. F. Horizontal section through the tectum combined from 
numerous sections. The types of cells are lettered as in the text. 
dec.d dorsal decussation ; nuc. magn nucleus magnocellularis ; tr. op tractus 
opticus fibres. «a part of a frontal section of the tectum, showing the 
torus semicircularis Halleri (torus s. H). Compare with Phot. 18. bdl.y 
bundle y to valvula; #r.t-cer tractus tecto-cerebellaris; tr. tecto-bulb and 
tr.b-tect tracts to and from the medulla among which the neurites of 
cells in the torus semicircularis run. 
Fig. G. Tectum opticum. Cell of the II type. 
Fig. H. Frontal section of the base of the mid brain through the 
decussation of the bundles of Muynert (dec.b. M). ac.arc arcuate 
fibres from the acusticum; bdl.a bundle of fine fibres from the medulla 
which decussates with Mrnynert’s bundles and ends in the same nucleus; 
c.ans commissura ansulata; nuc.b. M end-nucleus of the bundles of 
Meyxerr. 
Fig. J. Horizontal section through cephalic part of tectum and 
the base of the epiphysis. «a epithelium of the base of the epiphysis 
on a larger scale (inverted in relation to the main figure); dec.d dorsal 
decussation; ep.c epiphysial commissure; ep.s epiphysial sac or enlarged 
