SAKGEXT: the optic EEFLEX ArPAKATUS OF VERTEBRATES. 213 



along the median ventral groove of the torus, but mostly at the anterior 

 end. This is shown in Figure 55, where numerous fine axons (/as. 

 lieis.) from the cells of the torus are seen entering the ventricle in the 

 median groove of the torus-lobes. As development proceeds, the separate 

 axons become aggregated into bundles. In the adult the axons enter 

 the groove as five or six bundles (Fig. A", frt. tor. fbr. Reis. p-), "which, 

 running ventrad and caudad, unite with a similar bundle from the 

 opposite side. 



'cras.e'cnd. 



Figure J. Tautogolabrus adspersus, adult. Diagrammatic transverse section of 

 the anterior median dorsal portion of the mesencephalon and torus longitudi- 

 nalis, through tlie posterior commissure. The end apparatus of Eeissner's 

 fibre is projected on a plane. (In this figure, for trt. lor. fbr. Reis. a., read trt. 

 tor. fbr. Reis. p., and vice versa.) For meaning of abbreviations, see Explana- 

 tion of Plates, p. 257. 



The cells from the more lateral and anterior portion of the torus send 

 their axons into the ventricle through the posterior commissure or just 

 anterior to it. In young larvae before the development of the commis- 

 sure this is the shortest path to the ventricle (Fig. 56, trt. for. fbr. 

 Reis. a.), and the axons penetrate to the ventricle as a rule singly. As 



