\'. KuPFKEK, Cranial Nerves of \'ertebrates. 21^3 



prcebranchialis disappear, and the sole ones remaining are the 

 N. suprabranchiales. 



As such may be regarded: (i) The N. olfactorius (I seg- 

 ment), more clearly so after it was shown, through the olfac- 

 tory buds discovered by Blaue, that the organ of smell 

 belongs to the system of the lateral line, /.c, the branchial 

 sense organs. 2. The ophthalmicus profundus (II segment), 

 whose meso-cephalic ganglion (Gn. ciliare, Van Wihje, His) 

 fuses with the epidermis close above and behind the eyes; 

 later this root unites with that of the trigeminus, and the Gn. 

 meso-cephalicum with the Gn. Gasseri.(') 3. The acusticus 

 (VI segment), which is regarded as a remnant of a segmental 

 nerve. The development of the nerve, of its ganglion, and 

 of the ear, corresponds essentially to that of the homodyna- 

 mous parts of complete segments. The auditory vesicle is 

 the persistent, functionally modified branchial sense organ; 

 the pertaining segment remains in the hyoid arch. Whether 

 the aborted gill cleft is to be found, as Van Wihje thinks, 

 behind the facial, or, as Dohrn takes it, is to be sought before 

 the hyoid cleft, remains undecided. 



Regarding the relation of cranial to spinal nerves. Beard 

 at first declared himself in complete agreement with Froriep 

 in so far as the dorsal roots and ganglia of the one could not 

 be homologized with those of the other. Possibly Balfour 

 was right, that the cranial nerves showed a more primitive 

 condition than the spinal nerves, but it may be doubtful 

 whether the spinal nerves ever had the same primitive char- 

 acter-(^) Later he changes this opinion, and, in regard to the 

 supposed similar method of formation of the first ganglion 

 rudiment in head and trunk, declares that there is a partial 

 homology between the neural ganglia of the head and the 

 spinal ganglia, but the first might possibly be only homolo- 

 gous with the sympathetic portions of the latter(*) 



1 Anat. Anz., 1887, p. 565. 



2 Quart. Jour. Mic. Sc, Vol. XXVI, 1886, p. 142-143. 



3 Quart. Jour. Mic, Sc, Vol. XXIX, 1889, p. 153. 



