Herrick, Tactile Centers of Prionotus. 309 



as in teleosts generally. The tracts which I here term dorsal 

 funiculi are apparently chiefly descending secondary fibers from 

 the accessory lobes. It is doubtful whether either here or in the 

 region of the accessory lobes there is any considerable true funic- 

 ulus dorsalis as that term is used in higher vertebrates, though 

 the scattered bundles of root fibers and secondary tracts which 

 permeate the dorsal cornu and, farther cephalad, the accessory 

 lobes in a general way correspond with the dorsal funiculi. 



As the sections are followed toward the head, at the level of 

 the fourth spinal nerve the grey matter of the dorsal cornu 

 becomes still more greatly enlarged, the sensory root of this nerve 

 terminating in the center of this dense mass of neuropil. Head- 

 ward of the fourth nerve the dorsal cornu becomes more compact 

 with bundles of well medullated fibers scattered within the neuro- 

 pil, the whole complex occupying the dorsal third of the cross- 

 section of the spinal cord. Large, medullated tracts of descend- 

 ing fibers run from the dorsal cornu into the dorso-lateral fascicu- 

 lus and fasciculus proprius of the same and opposite side, the 

 latter crossing in the dorsal commissure. Both dorsal and ventral 

 commissures are very small in this region, the latter especially 

 being no larger than usual in fishes with spinal cords of the usual 

 form. As we approach the last (sixth) accessory lobe the medul- 

 lated fiber tracts in the dorsal cornu increase in number, many 

 of these fibers crossing in the dorsal commissure, which increases 

 in size, and the grey matter accumulates chiefly at the dorso- 

 lateral, border, where it is overlapped by the accessory lobe, with 

 which it becomes continuous a little further cephalad. 



Meanwhile the dorso-lateral fasciculus has retained its original 

 form and position, as have all of the more ventral structures; but 

 the tract occupying the position of the dorsal funiculus is repre- 

 sented by a small area of compact medullated fibers bounded 

 laterally by the dorsal cornu and accessory lobe, with both of 

 which it is connected by transverse medullated fibers. A short 

 distance farther headward the dorsal cornu fuses with the lateral 

 border of the accessory lobe, the median portion of the lobe being 

 free from the underlying tissue. 



The accessory lobes vary somewhat in appearance in different 

 specimens. Morrill follows Ussow ('82) and enumerates six 

 of these lobes. Their number in Prionotus might be counted as 

 one or two more or less depending upon whether account is taken 



