344 Journal of Comparati\e Neurology. 



region of the cerebrum, and from the ventral patch of white 

 matter the short and stout olfactory nerves pass to the bases 

 of the first named. 



In an early post-larval stage ^ the anterior commissure is 

 situated farther forward, and is broader than in the earlier 

 stage. The third ventricle passes for a considerable distance 

 in front of the commissure, and the cerebrum appears in 

 transverse section as a vesicular mass with dorso-lateral 

 patches of white matter; from the latter the olfactory nerves 

 pass forwards and outwards to the nasal sacs, now removed 

 some little distance from the cerebrum and disposed partly 

 in front of it. 



In the stage onc-half-inch long, the crebrum has under- 

 gone a further upward rotation, and the olfactory lobes are 

 now seen as bulbous masses projecting from the front end. 

 From the anterior ventral edge of each lobe the olfactory 

 nerve passes toward the nasal mucous membrane. Each 

 olfactory lobe consists, histologically, of fibrous matter, with 

 a few scattered deeply staining cells, and a narrow peri- 

 pheral margin. It is constricted at its point of origin from 

 the cerebrum, as in later stages, but its height is as yet 

 insignificant. 



In the stage three-fourths inch long, the olfactory lobes 

 are more elongated than in the last stage, and the constriction 

 at their point of origin is better marked. A transverse com- 

 missure unites their bases. The olfactory nerves turn outwards. 



[The commissure above mentioned can hardly be other 

 than that we have identified with the corpus callosum.] 



Upon the general question of the nature of the olfactoiy 

 lobe and fibres, the following remarks are quoted from 

 K511iker:(') 



" In my studies upon the development of the organs of 

 smell in human embryos(-) I discovered that the olfactory, 



1 KiJLLiKER, A., " Ueber die erste Entwicklung der Nervi olfactorius," Sitzungs- 

 berichten der Wiirzburger phys. med. Gesellschaft, 1890, XIV Sitzung von 12. Juli. 



2 Kiil.LlKER, A., Festschrift fiir Ziirich, 1883. 



