STRUCTURE AND DEVELOPMENT OF REISSNEE’s FIBRE. 99 
Tnacli more rapiHly than does formalin I was rather surprised 
to find that while the formalin-preserved material gave me 
quite good results the spirit maten’al was much less satisfac- 
tory. I can only suppose that tin’s latter had been dead for 
some time before preservation was attempted. 
Text-fig. 8, which, like the corresponding figure of Bdello- 
stoma, was obtained by superposing camera drawings of 
several adjacent sections, represents diagrammatically the 
condition of the brain of Myxine as seen in sagittal section, 
and the course of Eeissner’s fibre through the ventricles. 
Text-fig. 8. 
26 27 
A diagrammatic median sagittal section tlirongli the brain of 
Myxine glutinosa. (The lines 26. 27 indicate approximately 
the planes of the transverse sections reproduced in Figs. 26 and 
27.) c.c. Canalis centralis. i.c. Isthmic canal. uifd. 
Infundibular cavity, op. Optoccel. p.c. Posterior commissure. 
r.f. Reissner's fibre, s.c.c. Sub-commissural canal, a.c.o. Sub- 
commissural organ. s.?/(. Sinus mesocoelicus. r.c. Ventri- 
cular canal. HI. Third ventricle. IV. Fourth ventricle. 
Like that of Bdellostoma, the brain of IMyxine is 
exceedingly variable, but iu none of the three brains exa- 
mined has there remained any trace of an open connection 
between the ventricles of the fore- and mid-brain. 
In the mesocoel in every case five distinct chambers could 
be recognised. A well-marked sub-commissural canal 
^.N. c. c.), completely invested by the highly specialised epi- 
