496 JULIA B. PLATT. 
the primitive ridges connected with the trigeminal, facial, and 
vagus Anlagen. These ridges are formed not alone by increase 
in the number of cell layers composing the ectoderm, but also 
by increase in the depth of the cells themselves. The latter 
fact would be more evident in the figures had a longer strip 
of ectoderm at either side of the ridge been included in 
the drawing. The change in the depth of the cells is a 
gradual one. 
The long axis of a nucleus usually corresponds to that of the 
cell, and the long axis of an ectoderm cell lies usually either in 
the direction in which the cell is migrating if it be migratory, 
or in the direction of the transmission of energy if it be 
nervous. As both the path of migration and the line of trans- 
mission of energy in the posterior part of the vagus ganglion, 
through which fig. 4 cuts, are parallel to the long axis of the 
embryo, the cells composing the ganglion changed the direction 
of their axes on leaving the ectoderm, and the section which 
passes through the long axis of the cells in the deeper layers 
of the ectodermic ridge cuts across that of the ganglion 
cells. 
In Pl. 38, fig. 1, a commissural connection between the 
glossopharyngeal and vagus ganglia is seen a short distance 
below their respective roots. This commissure is formed from 
cells of the neural crest, which at first extended as a con- 
tinuous sheet from the beginning of the glossopharyngeus to 
the posterior limit of the vagus Anlage. The cells of the crest 
in migrating down the side of the brain divided into two 
groups, in each of which the long axis of the cells corresponds 
to the direction of the migration, and is consequently vertical. 
The two groups remain connected with one another, however, 
by a short commissure, which, serving possibly to transmit im- 
pressions from one ganglion to the other, is composed of cells 
with axes parallel to the long axis of the embryo, or at right 
angles to the axes of the cells composing the main vagus and 
glossopharyngeal ganglia. 
The fusion of the vagus ganglion with the ectoderm begins 
immediately posterior to the commissure, and a mass of ecto- 
