MOTOR NUCLEI IN PHYLOGENY 263 
In Cacatua roseicapilla the rostral extremity of the nucleus 
intermedius XII is practically on a level with that of the dorsal 
motor vagus nucleus, a relation similar to that obtaining between 
the motor vagus and hypoglossal nuclei in many mammals. 
Unlike the latter forms, the caudal extremity of the nucleus 
intermedius XII in C. roseicapilla extends relatively far below 
that of the dorsal vagus column. Cacatua differs from the 
other birds examined in these respects, as well as in the greater 
relative length of its nucleus intermedius XII and in the excep- 
tionally rostral level at which the first hypoglossal rootlet makes 
its exit (ef. figs. 15 D and 16). 
So far as can be gathered from Brandis’ descriptions and 
figures, the relations of the nucleus intermedius XII in C. gala- 
tea, Melopsitticus, and Palaeornis are very similar to those in 
C. roseicapilla. It would seem, therefore, that in parrots the 
specialization of a central hypoglossal intermedius cell group 
has progressed under influences which differ in some important 
fashion from those operating to produce what may be termed 
the typical avian intermedius cell complex. 
It has already been noted that the cell group here termed the 
typical avian intermedius complex has probably been evolved 
largely as the central expression of a peripheral specialization in 
the sound-producing apparatus peculiar to birds wherein a special- 
ized somatic syringeal musculature works synergically: and 
coordinately with a simple visceral laryngeal musculature. If 
this be so, it will be of interest to inquire if any peripheral special- 
izations of the syrinx or other organ obtain among parrots which 
might account for the presence in these forms of an intermedius 
XII nuclear development unique among birds.!! 
10 Bath (2 and 3) has shown that taste buds do not occur on the horny tongue 
epithelium of birds, though they are found in small numbers in the mouth region 
in the majority of these forms, chiefly near the entrance to the pharynx and glottis 
and in the mucosa of the buccal floor and margins of the jaws and to a lesser 
extent on the palate. In mammals Kappers (9) has pointed out that the distri- 
bution of taste buds innervated by VII and IX fibers over the surface of the 
tongue is to be correlated with the rostral and dorsal position of the hypoglossal 
nucleus close to the taste center of these forms. In parrots, however, though 
the total number of taste buds (i.e., 300 to 400) is much greater than in any other 
avian form, it is evident, in view of their location elsewhere than in the lingual 
mucosa, that incoming impulses from this source can play no such réle in deter- 
mining the location of the XIT nucleus. 
