The brain of Acipenser. 253 
Description of Plates. 
Pilates 213} 
The arrangement of the photographs in Plates 2—12 is determined 
in part by the relative intensity of the negatives, those of equal in- 
tensity being grouped together for purposes of reproduction. In all 
cases where not otherwise noted, the dorsal border of the photograph 
in frontal and sagittal sections and the cephalic border in horizontal 
sections is placed uppermost on the plate. 
Abbreviations. 
ac tuberculum acusticum 
ac.c large cells in tubereulum acusticum 
bal. Mey. or b. M. bundle of Mrynerr 
bdl.x bundle of fine fibres running forward in the medulla near the 
mid-ventral line to decussate with the bundle of Meynerr and 
end in the same nucleus 
bdl.y bundle from the base of the mid brain to the dorsal portion of 
the valvula 
c. a commissura anterior 
c.c cerebellar crest 
c.mam corpus mammillare 
c.p commissura posterior 
cereb cerebellum 
ch chiasma of the optic nerve 
com.c commissural cells in medulla 
com.inf. H. commissura infima Halleri 
d dorsal roots of cranial nerves 
dec.pop decussatio postoptica 
d.s dorsal sac or paraphysis 
epistr epistriatum 
f fimbria; decussation of granule neurites in dorso-caudal part of 
cerebellum, going to form cerebellar crest 
