The brain of Acipenser. 259 
Phot. 75. Fore brain. Cell of epistriatum. 120. 
Phot. 76. Two cells of epistriatum with neurites, showing how 
closely these cells are placed. Frontal section. X 120. 
Plate. 62: 
Phot. 77. Cell of epistriatum in horizontal section, showing den- 
drites spreading parallel with inner surface of epistriatum. 120. 
Phot. 78. Motor or cortical cells at extreme dorso-lateral angle 
of epistriatum. Lateral surface at right border of photograph. 120. 
Phot. 79. Cell of epistriatum. Branching of neurite. Frontal 
section, X 120. 
Phot. 80. Cell of epistriatum among fine fibre endings. X 120. 
Phot. 81. Lobus olfactorius. Spindle cell of granular zone, showing 
_ dendrites forming glomeruli. X 120. 
Phot. 82. Lobus olfactorius. Stellate cell of granular zone whose 
dendrite forms a large glomerulus. X 120. 
Phot. 83. Lobus olfactorius. Group of glomeruli borne by mitral 
cells whose bodies lie in adjacent sections. X 150. 
Phot. 84 Lobus olfactorius. Cell of Casar. X 120. 
ta ter leas 
Scheme of fibre tracts in the brain of a fish 30 cm in length 
The outline is drawn to scale at a magnification of 10 diameters, 
following Phot. 4 I have not aimed at great accuracy in representing 
the fibre tracts, since this would be impossible owing to the small 
space in which so many tracts must be shown. Several of the minor 
tracts could not be shown, and such omissions are noted in the text. 
The text also contains descriptions of the plate in connection with the 
various tracts. 
In the color scheme I have regarded the reflex are as consisting 
of a chain of several links. For these links I have used the colors of 
the spectrum, representing the sensory nerve roots by blue and the 
motor roots by red. Central sensory tracts of the first and second 
order are represented by green and yellow respectively. Descending 
tracts which carry impulses to the motor nuclei are shown in orange. 
Between the central sensory or ascending, and the central motor or 
descending tracts there are a variable number of links in the reflex 
chain. Some of these are merely connecting links, as is probably the 
ascending portion of the tractus strio-thalamicus. Others are commis- 
sural tracts, connecting similar nuclei of the two sides. Others may 
be called coördinating tracts, serving to carry impulses in indirect paths 
to the motor nuclei, e. g. the tractus tecto-lobaris. All these con- 
necting, commissural, and coördinating tracts, so far as represented, 
are drawn in sepia. The cerebellar part of the tractus lobo-bulbaris 
Te 
