S3 

 it v»9r8 no'."» possible to wsavs to^sthsr a fe« scHtterjJ threais 

 ia the 3\/olntiori of the cerebellum. Schaper ('94) has callel 

 attention to certain facts in the srnbryolofiy of the teleostean 

 cerebellum which nay be taken as the starting point. The cere- 

 bellurn arises in ontogeny, not as a brain-segment having the 

 fall value of the others, bat as a paired thickening in the 

 parietal walls of the neural tube at the anterior end of the 

 oblongata. These thickenings grow upward and mest, each other 

 in the nedian line. Schaper has since extended his studies 

 to all classes of vertebrates, and he finds ( '99) that the an- 

 teriDr limit of the bilaterally symmetrical anlage may be def- 

 initely fixed, coinciding with the boundary between the pri- 

 mary mid- and hiadbriin vesicles. The posterior limit of the 

 future cerebellum is by no means clear, however, for it seems 

 to merge backward into the oblongata. These are certainly 

 significant facts. 



It was shown in Section IV, Subsection 7, that the molec- 

 ular layer of the cerebella-n is continuous with the cerebellar 

 crest of the tuberculum acusticum, maintaining essentially the 

 same morphological characters throughout. It was also shown 

 that there are present in the taberculam acusticum neurones 

 which are identical with those of the cerebellum — molecular 

 neurones, granular neurones, and Purkinje neurones; the last 

 two varieties are not grouped into definite strata, however. 

 The presence of granular neurones in the acusticum is worthy 

 of remark, but the greatest weight must be attached to the 



