52 



'Journal of Comparative Neurology and Psychology. 



polated between the anterior palatine and the buds lying on the 

 roof of the pharynx at the point where the first gill arch joins 

 the roof. 



13. CERATOBRANCHIAL AND ROOF GROUP. 



This group consists of buds situated on the ceratobranchial 

 bar, the pharyngeal cartilages and the roof of the pharynx. 



The dorsal side of each ceratobranchial is innervated by the 

 dorsal branch of the post-trematic division of the ninth or tenth 

 nerve; the dorsal side of the first gill arch by the dorsal branch 

 of the ninth and the second, third and fourth by the same branches 

 of the second, third and fourth divisions of the tenth nerve. The 

 posterior demi-branch behind the fourth gill slit is innervated 

 by the ventral pharyngeal branch of the fourth division of the 

 tenth nerve in Menidia, 



As stated above, the first buds to appear on the gill are situ- 

 ated on the distal portions of the ceratobranchials of gills i, 2 

 and 3. From this point they spread proximally^, or dorsally, 

 until in series O' they reach the pharyngobranchials. Table 

 XVII shows the time of appearance of buds on the pharyngo- 

 branchials and the roof of the mouth. 



TABLE xvn. 



Table showing time of appearance and extent of buds on the pharyngobranchials, the extent indicated 

 by the section numbers between which buds are found. 



In series O' and P all buds are found on the pharyngobran- 

 chials and there is no overlapping, the groups being quite dis- 

 tinct; but in O there are 28 buds present in the roof of the 

 pharynx, only 18 of which are catalogued and shown in the 

 table, the remaining ten being scattered between the pharyngo- 

 branchials. In Q the first, second and third pharyngobranchial 

 groups overlap, since the cartilages do, so that in Q we have a 



