88 EDWARD PHELPS ALLTS, JUN. 



though indirectly, that the ampullai'y organs do represent 

 the terminal buds of ganoids and teleosts, and not the pit 

 orofans. As, in this research, I was also led to trace the 

 other cranial nerves of the region under consideration, and as 

 my observations differ in certain respects from, and complete 

 in others, the results of earlier writers on the subject, I have 

 thought best to fully describe, not only the lateral canals of 

 the head and the ampullary canals, but also the facial, tri- 

 geminal, and eye-muscle nerves, notwithstanding the fact 

 that there will necessarily be, in these descriptions, a certain 

 amount of repetition of well-known facts. 



The embryos nsed for the investigation were kindly sent 

 me by the Naples Zoological Station, and varied from 36 mm. 

 to 12"2 cm. in length. As I have no one at present in my 

 laboratory who could properly section these embryos for me, 

 I appealed for help to Prof. Gr. B. Howes, of the Royal College 

 of Science, London, and he most kindly undertook to have 

 them sectioned, under his personal supervision, by his pupil, 

 Mr. H. H. Swinnerton. Sections of 36 mm. and 55 mm. 

 embryos were first prepared, but these embryos were found 

 to be much too young for the purpose, and one of the largest 

 ones I had — a 12'2 cm. one — was selected. This last size 

 pi'oved an excellent one for the purpose in view, and the 

 following descriptions relate entirely to it unless otherwise 

 stated. Two different specimens of this age were sectioned, 

 one from the anterior end of the snout back nearly to the 

 first gill slit, and the other from the hind edge of the eye 

 back a certain distance beyond the spiracle. This second 

 specimen was sectioned in the hope that I might in it deter- 

 mine the ultimate distribution of the dorsal branch of the 

 glossopharyngeus, which I had been unable to follow in the 

 first specimen. I unfortunately could not follow it in the 

 second specimen either, the tissues being slightly brokeu at 

 a place where the nerve apparently enters the lateral edge of 

 the cranial extension of the trunk muscles, and the nerve 

 there lost in the displaced muscle fibres. 



All of the embryos sectioned were, at Prof. Howes' 



