\'. KiPFFKR, Cranial Nerves of }'i'rtcl}rates. 363 



All other questions bearing further upon the peculiarities 

 in this process appear to me at the present not ripe for dis^- 

 cussion. Yet I believe I may say one thing definitely, that 

 the rudiments of the dorsal nerves, as w^ell in the earliest 

 phase of the cell chains as also later, when fibrillae have 

 already appeared, alw^ays show the connection with the 

 central organ. 



According to what has been hitherto communicated, there 

 enter into the composition of the cranial nerves two systems, 

 the spinal and the hrafichial. The first is common to the 

 head and trunk; the latter appears exclusively in the head, 

 is most developed in the fore gill region, and one part is pro- 

 duced into the hind gill region. 



Concerning the spinal system of the head, I thus confine 

 myself here to the dorsal rudiments, reserving the ventral 

 spinal nerves for later mention. The complete interruption 

 of the roots between the regions of the trigeminus, acustico- 

 facialis and vagus self-evidently also affects the spinal system. 

 It also divides, therefore, into three regions, of which the 

 hindermost adjoins the spinal system of the trunk. Proceed-, 

 ing from the root-border, the rudiment of a spinal nerve 

 divides into two tracts. The lateral tract (zug) remains in 

 connection with the dorsal border of mesoderm — I denote it 

 as the dorsal branch of the dorsal spinal nerve — the median 

 tract, or ventral branch of the dorsal spinal nerve, passes 

 between mesoderm and brain towards the chorda, passes 

 around this and arrives at the outer side of the aorta. At 

 first consisting of serially arranged cells, this tract includes 

 in itself the rudiments of the spi)ial gafiglia and of the sym- 

 pathetic ganglia (Fig. 6). 



So far as I have been yet able to discover, the spinal 

 spinal system of the head does not keep pace in further 

 development with the branchial system, but instead under- 

 goes remarkable reductions. 



The nerves of the branchial system are, in respect to their 

 mode of origin, more composite. The rudiments proceeding 



