Landacre, Taste Buds of Ameturus. 51 



the area on the roof occupied by buds of the posterior palatine 

 group, which is from section no to 170. On the floor of the 

 pharynx we have the mid-ventral group, beginning at 93 and 

 extending back to the beginning of the oesophagus. The mid- 

 ventral buds, of course, furnish the ventral portion for the gills 

 as well as for the hyoid arch. 



Fig. I on Plate I will make these relations somewhat clearer. 

 It will be seen from this diagram that the distal hyoid buds 

 really represent a continuationof the anterior oral group rather than 

 the beginning of the pharyngeal groups. 



The distal hyoid group is a part of the posterior palatine group 

 structurally, that is, in time of appearance, and doubtless func- 

 tionally also, for it is difficult to see how buds lying on the roof, 

 floor and sides of the pharynx could fail to be stimulated at the 

 same time, since they lie in practically the same area measured 

 on the longitudinal axis of the embryo. The innervation of the 

 distal portion of the hyoid is from the ventral post-trematic 

 'branch of the ninth which enters it at the point of union with 

 the copula and runs proximally. 



The posterior palatine and proximal hyoid group, on the 

 other hand, are innervated by the r. palatinus posterior VII 

 and the mid-ventral buds in front of the union of the first gill 

 arch with the copula are supplied by the same nerve as the dis- 

 tal hyoid group. 



Probably no better illustration of what is meant by functional 

 groups or areas in the appearance of taste buds could be given. 

 This area is composed of four subdivisions having definite 

 anterior and posterior boundaries and is so situated that it would 

 seem to function as a unit. Portions of it are innervated from 

 the seventh and other portions from the ninth nerve. The hyoid 

 arch in particular has these two nerves supplying it, the former 

 going to its dorsal or proximal portions and the latter to its 

 distal or ventral portions. The distal hyoid buds represent the 

 posterior continuation of the oral group in point of time and not 

 at the beginning of the pharyngeal group. 



In series O, P and Q the dorsal buds are represented by the 

 anterior palatine group only, the ventral buds by the mid-ventral 

 group and the lateral area by the distal hyoid group, there being 

 a vacant area on the proximal hyoid which later is occupied by 

 that group of buds. On the roof the posterior palatine is inter- 



