I/O Journal of Comparative Neurology. 



his supposition will sometime ,be found to be true. What con- 

 nections are made by the fibers mentioned as covering the outer 

 surface of the structure, I am not prepared to say. 



THE association FIBERS OF THE PROTO-CEREBRON. 



The fibrillar substance of the regions surrounding the 

 bodies already described, or the rest of the central proto-cere- 

 bron, is composed of the association fibers coming from, and the 

 tracts of fibers going to, these bodies, together with bundles of 

 fibers entering it from various groups of cells and giving rise to 

 a great number of irregular fibers to be classed under the gen- 

 eral term of association fibers. In only a few cases have the 

 cells from which these fibers originate been impregnated along 

 with their fibers so as to make their relationships perfectly clear. 

 What little has been learned I have endeavored to bring out in 

 the diagrams that follow as well as in the camera sketches in 

 the last two plates. 



The fibers, as may be readily seen in fig. i, take various 

 courses, binding the upper, the lower and the lateral parts to- 

 gether. Fibers originating from cells above the antennal lobes 

 pass up on the inner side of the anterior roots of the mush- 

 room bodies and branch arborescently in the region just above 

 them (fig. 31 and fiber 10 in the diagrams). Just below the 

 root a small branch is given off that passes outward horizon- 

 tally. Other fibers seen in preparations by the copper-haema- 

 toxylin method in front of the plane of fig. i seem to originate 

 from cells above the antennal lobes, and, after passing upwards 

 near the median line as rather large fibers, bend over the ante- 

 rior roots of the same side and become lost in the fibrillar sub- 

 stance (PI. XVII). The fibers of the cells in the median line 

 under the edges of the calyx-cup and in front of the central body 

 also seem to branch in this region, for I find no indications of 

 their forming a chiasma and passing into the lower regions of 

 the brain as described by Viallanes ( 84) for the Orthoptera, 

 and by Cuccati ( gs) for Souuvnya. Other fibers of unknown 

 origin (fig. 40, PI. XXII), but of a very conspicuous appear- 

 ance branch rather profusely in this region of the fibrillar sub- 



