44 'Journal of Cojnparative Neurology and Psychology. 



relative times at which communis fibers are found in these rami 

 of the V' and VII nerves. 



The spreading of buds from anterior to posterior and their 

 appearance in detached groups have been sufficiently emphasized 

 in the discussion of these groups. The real significance of these 

 two facts when brought into relation with the nerve supply will 

 be discussed later. In connection with this table, it is of interest 

 to note that these groups are not determined solely by the nerve 

 supply, although in some cases groups are indicated by the nerve 

 supply, as in the two palatine groups. There are, however, 

 enough of these groups which either have several nerves supply- 

 ing the group or else branches from the same nerve supplying 

 two groups to indicate that the fundamental fact is the anterior- 

 posterior spreading. 



The appearance of buds on the peripheral distribution of the 

 nerve earlier than on the proximal distribution, which is of so 

 frequent occurrence, seems to be subservient to the anterior-pos- 

 terior spreading, since it is reversed in the case of the body buds 

 which lie posterior to the origin of the nerves. 



The smaller subdivisions of the units or groups are deter- 

 mined in almost all cases by the number of the nerves supply- 

 ing these subdivisions and by the fact that thev appear nearly 

 simultaneously. They are characterized briefly by being slightly 

 discontinuous but usually simultaneous in time of appearance. 

 The units, on the other hand, are never continuous with adjoin- 

 ing groups at the time of appearance, and never simultaneous 

 with the time of appearance of adjoining groups. They diff'er 

 from the smaller subdivisions of which they are composed in the 

 character of the nerve supply also. Some, as the anterior and 

 posterior palatine groups, have a single nerve supply, while others, 

 as the opercular, have as many as five nerves, some of them from 

 the VII and some from the V. Still other groups are innervated 

 by nerves, some of whose branches innervate other groups far- 

 ther forward. 



The above facts seemed to the writer to furnish a clue, not 

 only to the origin of ectodermic from endodermic buds if such 

 prove to be the phylogenetic method, but also to the innervation 

 of ectodermic buds by communis fibers. The whole difficulty 

 lies in the latter condition, for if we can explain the innervation 

 of ectodermic buds by communis fibers the difficulty in the 



