Landacre, Taste Buds of Ameiurus. 33 



formed enough to ascertain their exact boundaries and the 

 mandibular lateral line curves dorsally in the posterior portion 

 of the operculum and buds distributed along this line have the 

 same general direction in spreading, so that it is not possible to 

 give these boundaries separately. However, in the 11 mm. em- 

 bryo three buds are found on v^hat I take to be the post-frontal 

 and squamosal regions, and in the 14I mm. embryo only one bud 

 is found in this location. 



A fourth division (D) of this group comprises buds lying on 

 the branchiostegal membrane. There is only one bud in this 

 position in the 11 and 14I mm. embryos. This group is inner- 

 vated, as mentioned before, by ramus hyoideus. 



The post-orbital and opercular group as a whole is isolated 

 structurally, as mentioned, by w^ell defined areas devoid of buds 

 lying between it and the groups situated anterior to it. Its isola- 

 tion in time of appearance is still more marked. Group (A) 

 which approaches in position most nearly the nasal group can 

 hardly be considered at the time of its appearance as continuous 

 with that group and the remaining subdivisions are still further 

 isolated from preceding groups. As to the homogeneity of this 

 group functionally, in the absence of experimental evidence and 

 apparently of the possibility of obtaining such evidence, we must 

 fall back upon the isolation in position and in point of time as 

 our only evidence at present. 



Its innervation by communis fibers running out through five 

 different nerves, while not different in principle from the ante- 

 rior groups (notably the dorsal and ventral lip groups), still 

 shows the greatest diversity of any of the oral or cutaneous 

 groups. 



One interesting fact in connection with this group is that it 

 occupies practically its whole territory at the time of its appear- 

 ance and of course little evidence of its spreading backward is 

 given, although in both the mandibular and ventral opercular 

 portions there is evidence that the group spreads posteriorly. 



