156 NERVE COMPONENTS OF BONY FISHES. 



in. — The ramus mandibular is. — The course of the proxi- 

 mal portion of the r. mandibularis VII after its separation 

 from the r. hyoideus as above described, dififers greatly from 

 that of the forms described by Stannius, a difference to be 

 explained, perhaps, by the excessive development of the 

 preoperculum in Menidia. The temporary separation of 

 this ramus into two portions (viz., the r. mandibularis ex- 

 ternus and the r. mandibularis internus) before entering 

 the mandible, is a common character in the bony fishes, 

 as appears from the works of Stannius ('49, p. 63) and 

 Vetter ('78, p. 479). In Cottus alone the two portions do 

 not re-unite (Stannius). 



In my preliminary paper ('97) I described the naked 

 organs along the opercular canal as innervated from the 

 communis component. In this I was unduly influenced 

 by the size of the fibres. These nerve fibres are scarcely 

 larger than those which supply terminal buds on the top 

 of the head, yet they are very heavily myelinated so that 

 they stain very intensely. I have since that time traced 

 them with great care in a number of specimens and am 

 convinced that in every case they arise from the lateralis 

 component (r. mandibularis externus) and not from the 

 communis (r. man. internus). The organs are, I believe, 

 to be regarded as more or less degenerate pit-lines. They 

 are smaller than the similar organs supplied by the r. 

 opercularis superficialis and this may account for the fact 

 that the nerve fibres supplying them are of smaller size. 



I agree with Ruge ('97, p. 216) that the peripheral rela- 

 tions of the facial nerve contribute nothing to the hypoth- 

 esis that a branchiomere was originally intercallated 

 between the hyoid and the mandible. If such a segment 

 ever existed, it has left as small trace in the adult periph- 

 eral nervous system as in the central. Neal ('98) has 



