MOTOR NUCLEI IN PHYLOGENY 265 
According to Brandis’ observations (13, p. 634-5), the avian 
accessory nucleus becomes continuous at its rostral end with the 
cell group which has been described above as the nucleus inter- 
medius. It would appear also that Turner’s observations (50) 
confirm Brandis’ description, since the latter author’s ‘nucleus 
dorsalis XII’ evidently corresponds to Turner’s ‘nucleus of the 
spinal accessory.’ The difference between the descriptions of 
Brandis and Lubosch (41) would also largely disappear if due 
allowance be made for the latter’s failure to recognize the mixed 
X-XITI character of the intermedius cell group. 
Though some variation, no doubt, obtains in the rostral 
relations of the nucleus accessorius in birds, it is improbable 
in view of Bok’s recent findings in Gallus (11) that this nucleus is 
in continuity with the dorsal motor vagus column in any adult 
avian form. In his careful ontogenetic study of the roots and 
nuclei of the vago-accessorius complex in the chick (lec., pp. 
511-512) the latter author has shown that the elements of the 
ventro-lateral vagus nulceus, together with those of the nucleus 
accessorius, originate from the dorsal motor vagus column and 
migrate ventro-laterad as one cell complex. Differentiation of 
these two nuclei becomes effected secondarily by the caudal 
migration of accessorius neurones. Thus, though the nucleus 
accessorius in both birds and mammals is primarily derived from 
the dorsal motor vagus column, yet it would appear that in birds 
its cells migrate first ventrad and later caudad to reach their 
final situation in the cord, while in mammals the reverse is true. 
Nerves IX and X. It has been noted above that no vagus 
component was identified in the intermedius nucleus of Cacatua 
roseicapilla, though in C. galatea, Palaeornis, and Melopsit- 
tacus, Brandis (1.c.) was able to demonstrate its presence. How- 
ever, in view of the great similarity in the peripheral, lingual, 
laryngeal, and syringeal equipment of C. roseicapilla and C. 
galatea, it is probable that my failure to identify the component 
has not been due to its entire absence, but rather to the very 
extensive development of the hypoglossal elements of this 
complex. 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 34, No. 2 
