148 Journal of Comparative Neurology. 



afferent pneumogastric root. To the left, isolated presentation of n. X and XII. 

 Neither the olives and cerebellum nor the fillet and pyramids developed. Stage 

 when only the segmental apparatus is plain. Roof of fourth ventricle (hind- 

 brain cavity) membranous. Lateral lamina receiving the "sensory " (afferent) 

 fibers of the nerve, and containing intermediate cells, cerebral afferent cells and 

 especially the Anlage for the cerebellar apparatus (olives and cerebellum). 

 Basal lamina with nucleus and nerve and numerous intermediate elements for the 

 formation of the substanta reticularis. Adapted from W. His, Zur Geschichte 

 des Gehirns, Fig. 21, p. 360. 



Fig. J. Central part of a spinal segment of Pristiurus. From Lenhossek. 

 Afferent elements blue, efferent elements brick red. Intermediate elements 

 omitted. Lateral lamina with the afferent terminations ; basal lamina with the 

 segmental motor neurones to the side of the raphe. 



Plate XIX. 



Fig. 6. General plan of the nervous system. Afferent segmental system 

 blue, efferent (motor) segmental system brick red; cerebral mechanisms, afferent 

 green, efferent carmine ; cerebellar mechanisms, afferent yellow, efferent not 

 shown. 



