6G3 



still further frontally the aspect changes again. The dorsal portion 

 of XII. dorsalis vanishes, the lateral portion of XII. ventralis again 

 appears, after which the latter combines with the rest of XII. dorsalis 



x: 



** ""^Z^ dorsalis 



. -KH 



ventralis 



Fig. 20. 



to make one large whole ; the cell-group nearest the raphe lias 

 grown greatly, on the one hand it has extended niedioventrally, on 

 the other hand it has approached close to liie ependyma ; the little 

 cell-groups between XII. and X. dorsalis occur inconstantly, not 

 unfrcquenlly a gradual parvo-cellular continuation of the nucleus 

 funiculi teretis can be seen into the nucleus intercalatus Staderini 

 over tlie tongue nucleus. The latter decreases rapidly in size; 168 

 sections frontally from the calamus it has disap|)eared ; the ventro- 

 lateral portion remains longest in existence. 



The oliva inferior of the giraffe appears in the lalero-ventral region 

 of the si)inal pole of nucleus XII. and soon grows strongly in a medial 

 direction, which medial portion presently curves upwards and begins 

 to form a powerful lamel growing in a lateral direction. Very soon 

 the olives from the right and left join at the raphe and a lidie 

 further forward we can clearly see a connecting olive in the rai)he. 

 Near the calamus the olives have again receded from the raphe 

 and the dorsal lamel loses itself in several cell-grou[)s lying one 



43 



Proceedings Royal Acad. Amsterdam. Vol. XVIII. 



