MUSTBl.US L^VlS. 211 



Goroiiowitscli (26) says that, in Salmo fario, the two 

 nerves called by him the nervus ophthalmicus superficialis tri- 

 gemini and nervus ophthalmicus profundus trigemini are both 

 developed from ectoderm cells proliferated from the sam 

 supra-orbital region of the ectoderm. As the profundus nerve 

 of these descriptions holds the position, throughout life, of a 

 ramus ophthalmicus superficialis, it might be here assumed 

 that this nerve contained the elements of the similarly named 

 nerve in Piatt's descriptions of Necturus, and that in Salmo 

 its descent to the typical profundus position had been simply 

 arrested, the nerve remaining where originally laid down. The 

 profundus nerve, as first laid down in Salmo, is, however, said 

 to be directly developed from ectoderm cells, and not from 

 cells that could in any way be attributed to the neural crest, 

 thus differing so markedly in this from the ophthalmicus pro- 

 fundus of Necturus, as described by Piatt, that the two nerves 

 cannot be considered as homologous. A marked difference 

 in the manner of development of this nerve in Salmo and that 

 of the ophthalmicus profundus of the chick is also noted by 

 Guronowitsch, who says (p. 81) : " Bei den Vogeln zeigt die 

 Entwicklung des Oplitlialmicus Stammes eine Abweichung, 

 inden der Nervenstannn })rim;ir im Mesoderme angelegt wird. 

 Der Ophthalmicus der Vogel bekommt audi, wie von mir be- 

 schrieben, ectodermales liildungsuiaterial durch eine Keilie 

 von Zellenvermehrungs-Heerden welche langs der Verlaufs- 

 richtung des Nerven zerstreut sind." What the exact 

 anatomical position of this ophthalmic nerve of the chick may 

 be I cannot find, but I presume it holds the position of a ramus 

 naso-ciliaris, which is I believe always that of a true profundus. 

 Marshall, however, says (41, p. 29), that it "passes under the 

 rectus superior but dorsal of the other eye muscles and of the 

 optic nerve," — a somewhat anomalous position. 



Neal (45), in Squalus, finds the ramus ophthalmicus pro- 

 fundus developed from two processes formed at the ventral 

 end of a descending line of neural crest cells. One of these 

 processes grows posteriorly, unites with the anlage of the 

 ganglion of the nervus trigeminus, and forms the basal por- 



