MM: OROAHfl Of i ur. 



the fundaments ol hrai.chi. v.hich n long 



mploto development. ' :ii:r. on t li- strength of his own 



bold admi ihle tiio interpretation that at those 

 plar> \\here fusion < TCUI > /, , ,mt>-rinl ] 



epidermis into deeper parts to share in the formation of m-r 

 tracts. I'.KAKD expresses himself still more precisely 

 tint tin- sensory in rvous elements of the whole j 1 nerxoiis 



H ditleivMtiations from the outer germ-layer, Hide- 

 out ly of tin- central ner\oiis system. 



The accounts here given concerning a c< . is^ea of develop- 



ment, of certain nerve-trunks \\ith the outer germ-la \ r to me to al 



an indication in favor of tin- hypothesis expressed by my brother and me. 

 that the sensory nerves of the Vertebrate^ may h ;i \,- a -on formed 



out of a sub-epithelial nervous plexus, sudi as ^\\\ exists in :iis of 



many Invertclirato. 



(3) The investigations of the last few years, which have been 

 carried out especially by BALFOUR, MARSHALL, KoLUKtt, \\"MIN:. 

 FRORIEP, RABL, and KASTSCHEXKO, have j>ioliu-c<l important results 

 concerning the development of the cranial nerves, their ivlatio: 

 the 1 lead-segments and their value as conipsired with spinal nerves. 

 On the brain, as well as on the >pinal c..nl, there ar: some 



of which are dorsal, some ventral. K\-:i at the tim when the 

 ln-aiu-jilate is not yet fully clo>c.l into a tule < 

 formed on either side, at the place of its U-ni into th- 



primitive epidermi>, a neural i hicli lit-riiis ratlin 



forward and may be traced on us uninterruptedly in a 



rior direction, where it is continuous with tho neural ridi;.- 

 of tin* spinal cord. When, somewhat later, the closure and the 

 detacliment of the brain -vesicles from the primitive epidermis has 

 taken place, the i id^e lie^ on the roof of the vesicles and is fused 

 with them in the median plane. Tho most of the cranial nerves 

 namely, the tri^nniinis with the ( la-s.rian ganglion, the acusticu> 

 and facialis with the ^anirlion acusticum and prol.ahly also the 

 lion ^enieuli, and the ^lo--opliai-yngeus and vagus with the 

 related i:an<:l ion jiiirulare and g. nodosum an- ditlVrentiated >ut of 

 this fundament in the same manner as the dorsal roots of the 

 spinal ner\es. The ner\e-. which emerge do i : : erwards shitt 



their origin downward along the lateral walls of the 1. rain \esicles 

 toward the base of the latin . 



All the remaining unenumerated cranial nerves oculoinotoriiis, 

 true-hit aris. aUlucens, hyi><>-io us, and accessor ins uro developed 



