304 



NEAL 



Fig. 9 A portion of a cross-section of a 13-mm. Squalus embrj'o cut in the 

 region of the sixth rhombomere, showing the primary relations of somatic motor 

 and splanchnic motor niduli. These are just the reverse of those described in 

 text-books. Subsequent migration (neurobiotaxis) brings them into the adult 

 position in relation to each other. 



Fig. 10 A section of the same embryo in the region of one of the anterior 

 roots of the abducens, showing the niduli of the facialis and of the abducens in 

 their primarj^ position. A compact bundle of neuraxons of the abducens passes 

 dorsal to the nidulus of the facialis. The left wall onlj' is shown. 



Fig. 11 A portion of the left wall of the medulla as seen in a frontal section 

 of a 13-mm. Squalus embr5'o, showing a portion of the nidulus of the facialis 

 (r.hyoideus). The neuraxon processes of the numerous neuroblasts extend ante- 

 riorly and I'aterally in the brain wall. They unite into a longitudinal fiber tract 

 which extends anteriorlj^ to the root of the facialis nerve. This fiber tract is 

 quite independent of the marginal veil of fibers. 



