4i6 Journal of Comparative Neurology and Psychology. 



portion among the chief tertiary cells (Fig. 23). The details 

 of the endings of the crossed fibers I have not been able to 

 observe, but there is every reason to believe that they are essen- 

 tially similar. 



I have no complete impregnations of the intrinsic commissur- 

 al neurones. The evidence is that their delicate, feebly medul- 

 lated neurites gather in the interior of the nucleus and termi- 

 nate after crossing among the dendrites of the chief tertiary 

 neurones of the opposite side. The layer of these chief cells 

 envelopes the secondary nucleus on all sides except where it is 

 interrupted by the secondary and commissural tracts. The 

 neurites of these cells pass directly outward and become medul- 

 lated as they enter the chief certiary tract for the inferior lobe. 

 Just external to the layer of tertiary neurones the gustatory 

 nucleus is encapsuled by a dense layer of heavily meduUated 

 nerve fibers. These are partly the tertiary fibers, but chiefly 

 cerebellar tracts. The position of the secondary gustatory nu- 

 cleus in the isthmus is such that the cerebellar penduncles, p.iss- 

 ing downward from the cerebellum and valvula, almost entirely 

 envelop it. It is this peculiarity which suggested to Mayser 

 the name "Rindenknoten." Surrounding this fibrous capsule 

 is an aggregate of nuclei with very diverse connections to which 

 Mayser applied Stieda's name, "Uebergangsganglion." 



This region is perhaps the most intricate and difficult of 

 analysis in the teleostean brain, as it contains several large cen- 

 ters and numerous important tracts, both meduUated and un- 

 medullated, all crowded into a very small space. The dorsal 

 part of the isthmus is more than usually crowded in these types, 

 not only by these great gustatory centers, but also by the en- 

 larged cerebellum and valvula and their associated tracts. 



The broad line of fusion of the valvula cerebelli with the 

 torus semicircularis (colliculus) is occupied by a very dense 

 mass of cells and meduUated and unmeduUated tracts whose 

 relations are only imperfectly shown in my preparations. The 

 whole complex, which lies mesially of the nucleus lateralis mes- 

 encephali (Edinger), or colliculus, I term provisionally the 

 nucleus lateralis valvulae. It is, apparently, the most cephalic 



