BRx\NCHES — BRANCHIAL NERVES OF FISHES 147 



the nerve hillocks of the laterosensory canals and to the sensory 

 cells of the nerve pits. Nachtrieb ('10) maintains that there are 

 no sensory cells related to these pits, and says that he never 

 found any of the branches or branchlets of the lateral-line nerves 

 in any way in communication with them. He accordingly con- 

 siders the pits to be simply secretory organs secreting a pecuhar 

 mucus, Kistler ('06) had, on the contrary, previously found 

 what he considered to be nerve fibers going directly to the cells 

 at the bottoms of the pits, and my work confirms this statement, 

 for I find, both in the adult and in the 140-mm. specimens, nerve 

 fibers going directly to the bottom of each of the many pits that 

 w^ere examined. Furthermore, no trace of mucus was found in 

 any of the pits of the 140-mm. specimens. It therefore seems 

 certain that these pits are, in part at least, sensory organs, and 

 it is equally certain that the nerves that innervate them are 

 quite largely composed of lateralis fibers. The branches that 

 supply the organs on the gill cover arise, however, from the 

 rami opercularis and hyoideus facialis, and not from the man- 

 dibularis externus, which supplies all the sensory organs in the 

 hyomandibulo-mandibular laterosensory canal. The branches 

 here concerned of the ramus opercularis apparently correspond 

 to that branch of the ramus opercularis superficialis facialis of 

 Herrick's ('99) descriptions of Menidia that supplies what that 

 author describes as small and scattered pit organs, but I know 

 of no fish in which the ramus hyoideus contains lateralis fibers, 

 unless it be Ameiurus. Herrick ('01) says of the latter fish 

 that the ramus hyoideus apparently only contains motor and 

 general sensory fibers, but adds that there are occasional termi- 

 nal buds and small pit organs in the branchiostegal membrane 

 which may be supplied by branches of this nerve, though he 

 could not trace fibers to them. In Gadus, Herrick ('00) de- 

 scribes a nerve which he says is clearly formed by the fusion of 

 the rami opercularis superficialis and hyoideus, and a minute 

 twig of this nerve is said to run downward, overlying the ramus 

 hyoideus, and to be distributed to pit organs. 



From the above it is seen that the nerve pits on the opercular 

 gill of Polyodon and the small pit organs of Ameiurus have mark- 



