922 THE AMERICAN NATURALLIST. [Vor. XXXIV. 
are identical upon the two sides, although they differ in the 
section, as the plane of cutting was not symmetrically trans- 
verse for the head. These structures are in the following 
order: 5, the trigeminal ganglion; 7.8, the acustico-facial gan- 
glion complex ; the otocyst, Oz., with upon one side the separated 
ductus endolymphaticus, D.Z., and upon the other side the 
opening of the ductus displayed by the section ; 9, the glosso- 
pharyngeal ganglion; 70, a portion of the vagus ganglion; 
12, one of the hypoglossal ganglia. Upon the left side of the 
figure the connection of the trigeminal ganglion with the angle 
of the wall of the hind-brain is demonstrated; by this connec- 
tion and by its large size the trigeminal ganglion may always 
be identified in the embryo. The brain-wall has a thin outer 
layer both in the hind-brain and mid-brain ; this is the outer 
neuroglia layer (Randschleier of His) and is conspicuous from 
the absence of stain; inside of the external layer the wall of 
the brain is crowded with nuclei, and therefore appears deeply 
stained in the preparation. Three neuromeres (/Vew.) appear 
in the section, each marked by a concavity on the inner side of 
the brain-wall. 
Fig. 3 is from section 195, and therefore ten sections below 
Fig.2. It is given to show three points not shown in the pre- 
ceding illustration: 1, the spinal accessory nerve root (Z7) 
arising from the cervical (in the figure, upper) end of the hind- 
brain and running forward to join the vagus ganglion; 2, the 
trigeminal ganglion with the internal jugular vein, which is cut 
twice (/ug.', /ug."), abutting close against it, —a very charac- 
teristic relation (this vein takes a sinuous course along the 
side of the hind-brain, for it passes inside the twelfth, eleventh, 
tenth, and ninth nerves, then outside the otocyst and the 
seventh-eighth nerve, and inside the fifth); 3, the infundibular 
process or gland (/zf.), springing from the floor of the fore- 
brain (£4). Attention may also be called to the structures 
(Str), resembling the strize acusticz, but which seem to be 
rather the fibres of the lateral root of the facial. 
The next figure (4) is from a lower level. The section passes 
through the eyes, the upper end of the auditory cleft (Fig. I, 
Au.), and the upper cervical region of the spinal cord. The 
