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bulletin: museum of comparative zoology. 



the commissure develops in thickness, this becomes a longer path, and 

 the axons become aggregated into fascicles and bundles. Later in front 

 of the tract this posterior commissure becomes much more closely con- 

 solidated. The tracts from each half of the torus are shown in Figures 

 / and A', passing through the anterior part of the torus and converging to 

 the median plane, where they emerge into the ventricle in one or two 

 separate divisions j\ist anterior to the posterior commissure. I have 

 been successful in getting this tract impregnated in Golgi preparations, 



cras.e'end. 



'^•-trt.tor.fbr.Reis.a. 



Figure K. Tautogolabrus adspersus, adult. Diagrammatic parasagittal section 

 of the anterior, median, dorsal portion of the mesencephalon. The end appa- 

 ratus of Reissner's fibre of one side is projected on the median plane. For 

 meaning of abbreviations, see Explanation of Plates, p. 257. 



though from a large collection of Golgi material I have gotten no 

 impregnation of other portions of tlie torus longitudinalis. 



Processes of another kind arise, usually from the dorsal sides of the 

 torus cells. These run dorsad and toward the median plane and collect 

 in fascicles, forming the tractus toro-tectalis (Figs. J, K ; Plate 8, Fig. 

 57, trt. tor. tcf.), which at the upper level of the torus turn outward into 

 the tectum. Some of the fibres mingle with those of the dorsal decus- 

 sation (jlec. cZ.), while others are lost in the tractus opticus (trt. ojd.) of 



