222 



In many Teleosts a large part of the surface of the hemispheres 

 is formed by the corpus striatum. Kappers (4) has described this 

 in Gadus and Hippoglossus. On the other hand, in Sjnbranchidae 

 the corpus striatum is almost completely pushed away from the 

 surface, owing to the septum growing over it from the median side, 

 and the epistriatum from the lateral side. Only a small portion of 

 the striatum remains on the surface, viz. on the dorsal side of the 

 hemispheres, lateral from the frontal point of the septum. 



As was already remarked (pag. 217), the cerebra of Monopterus 

 and Synbranchus are specially remarkable owing to the two 

 hemispheres having partially united (fig. 2). 



This junction has an important influence on the relation of the 

 ventricular cavities. 



The ventricular cavity dorsal and lateral from the two hemispheres 

 has been called ventrieulus lateralis by Goldstein (1), and the slit 

 between the hemispheres has been termed ventrieulus medianus by 

 the author. This nomenclature may very suitably be employed here, 

 now that the two ventricle portions have been separated by the growth. 

 Ventrally from the coalescence between the hemispheres lies the 

 ventrieulus medianus, for in spite of the growth the median ventricle 

 remains still clearly visible in these fishes, owing to the fact that the 

 hemispheres of the forebrain always deviate slightly from each other 

 on ihe ventral side above the lamina terminalis and the commissura 

 anterior. Behind the commissura anterior the median ventricle is 

 connected with the recessus pi'aeopticns, while at the frontal pole 

 of the cerebrum the lateral and median ventricles are continuous. 

 For the rest, the two ventricles are completely separated, also in the 

 front portion of the cerel)rum. Here the two halves of the fore-brain 

 lie closely pressed together, each indentation in the one half being 

 filled out by the other half, and we frecpiently see a blood-vessel 

 passing from the one side to the other (fig. 3). Locally too the two 

 halves have frequently grown together; such a coalescence is i-ather 

 larger immediately caudad from the bend in the sulcus limitans 



(fig- ^)- 



The caudal parts of the hemispheres have completely united. 

 The frontal boundary of this coalescence is not constant. In Mo- 

 nopterus it runs differently from that in Synbranchus; very probably in 

 individual cases it will not be constant either, and this is not sur- 

 prising, consider-ing the local coalescence, which can also be found 

 in the frontal portion. On the other hand, the boundary behind the 

 level of the commissura anterior is sharply defined' (fig. 2). 



Between the two hemispheres, on the dorsal side, is a deep groove, 



