SARGENT : THE OPTIC REFLEX APPARATUS OF VERTEBRATES. 219 



(1) iierve'Cells with characteristic nerve-processes, (2) a nerve-net 

 distributed through the whole area of the torus, and (3) ependymal 

 cells. The " cellules nerveuses speciales " (compare Fig. L) are globular 

 or pear-shaped, 10 to 14 micra in diameter, with a large nucleus, and 

 are irregularly disposed through the whole space of the torus. As a 

 rule there is but a single process from the cell, which at a short distance 

 from the cell divides. One of these processes is "plus delicat et plus 

 tenu," and may again divide. "II conserve un cours presque rectligne 

 et . . . se laisse suivre sur le longues portions vers la parti superieure 

 et externe du torus, . . . sur le point ofi le torus s'attache lateralement 



Figure L. Tinea vulgaris. Diagrammatic transverse section of the torus longi- 

 tudinalis and adjacent portion of the tectum of the riglit side. (Adapted from 

 Sala's Figs. 1, 2, and 3.) For meaning of abhreviations, see Explanation of 

 Plates, p. 257. 



avec le toit optique, . . . ou il contribue a constituer un faisceau de 

 fibres nerveuses qui, se continue lateralement dans le toit oj)tique." 

 This description corresponds with the fibres which collectively I have 

 called the tractus toro-tectalis (compare Fig. L, trt. for. tcf.). 



According to Sala this tract in passing out of the torus into the 

 tectum passes obliquely between the fibres of the dorsal decussation, 

 " fibres commissurales des lobes optiques," and " plie brusquement a I'ex- 

 terne et se dirige vers le toit optique, courant toujours sur un plan 

 un pen supericur a celui sur lequel courent les fibres commissurales." 



This fibre-tract from the torus to the tectum was first seen by 



