1 6 journal of Comparative Neurology and Psychology. 



later under the analysis of the smaller subdivisions of which these 

 are composed. So far as Tables II and III are concerned, the 

 cutaneous group may be considered as an extension of the oral 

 buds out over the upper and lower lips and so to the head and body. 

 It is almost impossible to tell whether a bud situated on the 

 anterior edge of the lip is to be counted a s oral or cutaneous. For 

 these particular areas buds above the dorsal boundary of the oral 

 epidermis ot the upper lip were counted as on the top of the head 

 and the same arbitrary rule was applied to those of the lower lip. 

 And while the appearance of buds on the body is by discontin- 

 uous groups, as will be shown later, we may consider them for 

 the present as simply extensions of the buds within the mouth 

 with which they are continuous at that point. 



The simultaneous appearance of the two primary groups and 

 their wide separation, one lying in the ectoderm of the extreme 

 anterior portion of the oral cavity and the other in the endoderm 

 of the pharynx, renders the exact determination of the anterior 

 limits of the pharynx unnecessary so far as this type is concerned, 

 at least. 



The anterior limits of the pharyngeal group are definite and 

 do not move forward, while the posterior limit of the oral group 

 moves steadily backward (see Table IV) until it reaches the 

 anterior limit of the pharyngeal group; and in the absence of 

 definite knowledge of the limits of the pharynx it is much more 

 probable that oral buds, as will be seen later, may spread into 

 endodermic territory than that the reverse process takes place. 

 Except for the spreading of the pharyngeal group back into the 

 oesophagus, it is much more constant in its position than the oral 

 and cutaneous groups, which in addition to spreading back in 

 the mouth also spread out from the lips and finally cover nearly 

 the whole surface of the body. 



These buds of the oral and cutaneous groups which are inner- 

 vated by the gustatory fibers from the geniculate ganglion show 

 a much greater adaptability to the functional needs of the organ- 

 ism than those of the pharynx which are innervated by the ninth 

 and tenth nerves. 



These three groups seem to represent three more or less well 

 defined functional groups of which the oral and cutaneous are 

 much more closely related to each other structurally and func- 

 tionally than are either of them to the pharyngeal; and it is in the 



