Houser, Zhe Neurones of a Selachian. 69 
the officials of the Marine Biological Laboratory for courtesies 
extending over a period of several years; and to Professor 
Brooks, I cannot do less than express my sincere appreciation 
of the numerous helpful suggestions given me during the com- 
pletion of my work. 
SecTION II. Review or EARLIER RESEARCHES. 
Z. Anatomical Work [Involving Errors of Interpretation. 
To trace the history of a misconception isa task upon 
which few can enter with even the least degree of enthusiasm, 
but it is necessary for us to notice briefly here certain erroneous 
views which have held sway relative to the homologies of the 
parts of the selachian brain.- The interbrain, and along with it 
the midbrain and often the cerebellum as well, have been vari- 
ously interpreted by the investigators of the last three decades. 
Mictucuo-Mac tay (’70) was the first to break away from the 
established teachings of von Barr (’37) concerning the possible 
homologies of the several brain-segments. Overlooking, in 
effect, the true interbrain entirely, since he regarded it as noth- 
ing more than a longitudinal commissure, MictucHo-MAcray 
identified the Zwzschenhirn in that segment which we know as 
the midbrain; the cerebellum, being next in the longitudinal 
series, consequently stood for his A/zttelhirn ; while he found his 
Fiinterjurn in the small inferior lobe of the true cerebellum. Such 
an interpretation appears almost inexplicable to us, but we 
must not allow ourselves to forget that the homologies so con- 
fidently traced by us to-day are grounded on many neurological 
studies, the results of which were not available to the investi- 
gators of the earlier period. 
Unfortunately for comparative anatomy, the conclusions of 
Miciucno-Mactay were accepted by GEGENBAUR, and were in- 
corporated by him in the second edition of his Grundzige (’70), 
and were continued in the smaller Grundriss (74). Appearing 
also, of course, in the French translation of the former work 
by Voer, and in the English translation of the latter by BELL, 
the errors were, ‘through these several channels, given the 
