54 'Journal of Coiuparativc Nnirology on J Psychology. 



also innervate the buds of the ceratobranchials. No buds <,p- 

 pear on the basibranchials until in series U, 89 hours after they 

 appear on the ceratobranchials, when two buds appear on the 

 first basibranchials, and two also on the second basibranchials. 

 In both cases they lie one on the right and one on the left side, 

 respectively. The later appearance of these buds which lie on 

 structures segmentally arranged and with segmental nerves is 

 difficult to explain unless it is due to the minute size of the basi- 

 branchials and their late differentiation, in which case, of course, 

 buds could not appear on them at the same time they appear 

 on the remainder of the gill structures. 



The limitations of this group even aside from its relations to 

 the gills are quite definite. It has a definite anterior-posterior 

 boundary which as late as series U has an area in front of it 

 devoid of buds dorsally; laterally no buds spread from the 

 dorsal or ventral portions of the gill out to the ectoderm. In 

 fact, there are no buds on the ventral or lateral side of the 

 isthmus in the 20 j mm. embryo from the point where the first 

 gill bar joins the isthmus back to the point where the oesophagus 

 closes. Here one bud was found, but the whole ventral area, 

 even in the 20^ mm. embryo, still further l)ack than this point, 

 is practically devoid of buds. Those present on the body lie 

 along the mid-lateral and dorsal portions. 



There seems to be little doubt that no buds move from any 

 portion of the pharynx out through the operculum to reach the 

 body. All body buds in Ameiurus represent extensions back- 

 ward of the surface buds lying farther forw^ard and all are inner- 

 vated by gustatory fibers from the seventh nerve. Herrick ('01) 

 does not mention any fibers running to the posterior portion of 

 the isthmus, but it is probably innervated by the fibers from 

 the seventh. If by fibers from the ninth, it would be the only 

 case in Ameiurus. How^ever, in Menidia the ramus lat. acces. 

 receives gustatory or communis fibers from the ninth nerve. 



14. THE MID-VENTRAL PHARYNGEAL GROUP. 



This group consists of buds lying exactly on the mid-ventral 

 line of the floor of the pharynx. Buds appear first on the floor 

 of the pharynx in series N somewhat later than those on the 

 gills, and in the region where the first buds appear on the dis- 

 tal hyoid group. They occupy about the same position on the 



