Herrick, Morphology of Brain of Bony F'ishes. 355 



by the writer as indicated above. (') Previous viniters have 

 either regarded it as absent or fused with the prascommissura. 

 In the latter view, proposed and defended by Osborn, the 

 present author coincided for a time, in spite of the grave 

 morphological objection that the callosum and hippocampal 

 commissure on the one hand and the prjecommissural svstem 

 on the other belong to distinct systems. The former are 

 cortical, the latter basal. It would be necessary, in a case 

 like that of fishes where the cortex is suppressed, to consider 

 that the axis of the cerebrum had been greadly modified and 

 shortened in order to bring the two systems into juxtaposi- 

 tion. No such supposition is necessary, for the callosum 

 and fornix systems are present and in just the position which 

 the nature of brain development would lead one to predict, 

 i.e., well forward near the union of pallium and axial lobe, 

 in close relations to the lamina terminalis and on the oppo- 

 site side the axial part of the ventricle from the callosum. 

 Fig. 8, Plate XXV, illustrates the relation. A glance at 

 Fig. 2, Plate XXIV, will indicate how distinct the two 

 systems are. It will also be noticed that the callosum is 

 intimately associated with the pyramidal cells of the central 

 lobe, which we insist upon as representing suppressed motor 

 cortical areas. Immediately caudad of the callosum are two 

 cellular projections into the ventricle, which in all respects 

 represent the corpus fornicis. A tract homologous with the 

 combined fornix and hippocampal commissure springs from 

 the hippocampal cells entad of the radix lateralis and passes 

 to the median line, part entering the fornix body and part 

 form a commissure caudad of but adjacent to the callosum. 

 There is a cellular interval between the two commissural 

 systems. There is a small tract arising in the fornix body of 

 either side destined for the thalamus. 



In the second part of Professor Osborn's valuable paper 

 on the corpus callosum (-) these words occur: " In regard to 



1 Journal of Comparative Neurology, pp. 164-16 



2 Morphologische.Jahrbuch., Band XII. 



