•can Naturah 



NOTES UPON THE ANATOMY AND HISTOLOGY OF 



THE PROSENCEPHALON OF TELEOSTS. 



By C. L. Herrkk. 



Our knowledge of the microscopic structure of the cerebrum 

 of bony fishes is very imperfect, and I -hall endeavor to show 

 that, notwithstanding the great progress recently made in de- 

 termining the difficult homologies involved, gross misconcep- 

 tions pass current at the present time. The fundamental diffi- 

 culty lies in the fact that the cortex is anatomically absent 

 though morphologically preset it. In < tther words, though there 

 is no functionally normal cortex, its place is taken by an epithel- 

 igerous membrane which in all important morphological par- 

 ticulars substitutes for it. It is quite a different question 

 whether the cortex is physiologically represented ; i. e., whether 

 cellular structures exist whiel i functionally replace the unde- 

 veloped cortical areas. Tins may rank among the most impor- 

 tant question of physiology as it undoubtedly is of morphology. 

 Inasmuch as the cortex of higher vertebrates serves solely as 

 the organ of consciousness in the limited sense, if it could be 

 shown that it is not only anatomically absent, but physi- 

 ologically unrepresented, we should have strong reason to sup- 

 pose that consciousness is practically absent in the group of 

 fishes and thus is an unnecessary element in a purely animal 

 existence even of a relatively highly differentiated organism. 



On the other hand, if it could be shown that some other cell 

 aggregate functions in place of the suppressed cortex, it might 

 be hoped that in locating the substituting areas we should ob- 

 tain the clue to the origin of the cortex and the law of devel- 

 opment or, rather, the archeteetonic plan of formation. In the 

 latter respect we have secured so much concurrent evidence 

 from widely different sources that the case scents: comparatively 

 clear. 



If the fish brain, iit spite of its great dissimilarity to the 

 brains of higher vertebrates is actuallv homologous with the 

 latter in detail, it should be possible to discover the exact 



