The brain of Acipenser. 63 
which not only fixes them to the slide but also prevents them from 
tearing when the dammar is spread over them. They are then 
dehydrated by two baths of the carbol-xylol mixture, and the car- 
bolic acid is completely removed by (at least three) changes 
of xylol. In covering with dammar, slow drying over a water bath 
or paraffin oven may be very injurious, while rapid drying at high 
temperature is perfectly safe. The temperature of red-hot iron is 
entirely harmless when only dammar or xylol-dammar is 
present, but the presence of the smallest quantity of carbolic acid 
is fatal. I therefore use hard or nearly hard dammar, heating both 
the slide and the dammar over the flame and spreading the dammar 
with a glass rod until a uniform smooth layer as thin as consistent 
with covering the sections is obtained. As soon as cold the dammar 
is hard and the slide is ready for storing permanently. Sections 
now nearly four years old are absolutely unchanged. The method 
is much more rapid and convenient than that by slow drying, and 
much safer. 
The GOLGI preparations comprise series of sections in the three 
conventional planes and some oblique, as follows: two frontal (trans- 
verse), three frontal inclined backward in the plane of the optic 
tracts, one frontal inclined forward in the plane of the bundles of 
MEYNERT, five horizontal, and six sagittal. 
The photographs accompanying the paper are reproduced from 
the negatives, the micro-photographs without any retouching. Photo- 
graphs 3, 5, and 6 have been slightly retouched to reduce the ex- 
treme blackness of the deep cavities. This does not affect the de- 
tails in any degree whatever. 
The manuscript of that part of the paper dealing with the hind 
brain, both descriptive and theoretical parts, was in its present form 
in May, 1899, except for references to papers which have been 
published or have come into my hands since that time. I have 
inserted full discussions of such parts of C. J. HERRICK’s paper on 
the cranial nerves of Menidia as bear upon my subject. To the 
large paper of HALLER on the brain of Salmo and Scyllium, however, I 
have made only a few brief references. This is for two reasons. First, 
as has been said by EDINGER (in: Bericht 1897—98, p. 64), HALLER’s 
nomenclature is so peculiar as to make his paper very difficult to un- 
derstand. Second, I have found so many statements in his descriptions 
which seem to me utterly at variance with all the results of modern 
investigations of the lower vertebrate brain that I have thought it 
