MOTOR NUCLEI IN PHYLOGENY 241 
of the nucleus intermedius X in relations that may be described 
as typically avian, since with but slight variation they have been 
found to obtain in the majority of the birds so far examined 
(fee, 16 pA, ByoG;,and:|D gps i260), 
As in Cacatua, the most rostral portion of the dorsal part of 
the posterior visceral motor column in Ciconia is occupied by the 
motor IX nucleus. The relations of this nucleus and the mode of 
origin of its emergent roots in the latter form differ but little 
from those already described in Cacatua and require no further 
description here. 
The dorsal motor vagus nucleus in Ciconia is much larger 
than in Cacatua and forms a conspicuous cell column which in 
the closed portion of the medulla occupies a position lateral and 
dorsal to the central canal within the periependymal gray and 
dorsal to the nucleus intermedius X and XII (fig. 2). 
At the junction of the medulla and cord and below the caudal 
end of the nucleus intermedius X, the dorsal visceral motor cell 
column becomes reduced in bulk and its elements become arranged 
in irregularly spaced cell clusters. 
In the same relative position the cell column, though discon- 
tinuous in places, was traced caudad a considerable distance. 
The origin of root fibers from the most caudal part of this nucleus 
was not demonstrated. The lower limit of the nucleus could 
not be definitely determined (fig. 16 C, p. 260). 
The more caudal of the fine rootlets which arise from this cell 
column pass almost directly dorsal to reach the periphery, and in 
this respect resemble emergent XI nerve roots (ef. Lubosch, 
41). The topography of the roots and nucleus of the latter 
nerve was not satisfactorily determined in Cacatua nor in Cico- 
nia, but in neither of these forms does it appear that the dorsal 
motor vagus nucleus becomes continuous with the accessory 
nucleus in a manner similar to that observed in reptiles (10), 
amphibians (9), and selachians (8). 
In Ciconia the nucleus intermedius X begins a short distance 
caudad of the exit level of the motor IX root as a ventral enlarge- 
ment of the dorsal motor X column. From the outset, however, 
the morphology of its cells serves to differentiate it from the latter 
