Neal. — Nervous Syst. Squalus. 



PLATE 8. 



Stages in the development of the nerves oculomotorius, ramus ophthalmicus 

 superficialis trigemini, and ramus ophthalmicus profundus trigemini. 



Fig. 58. A frontal section of an embryo with 5-5 somites (8i-9 mm.). Embryo 

 killed with Davidoff's fluid. Tlie oculomotorius appears as a cellular 

 strand extending from tiie inner side of tlie mesocephalic (profundus) 

 ganglion to the wall of the midbrain. Magnified 500 diameters. 

 Reconstructed from three sections. 



Fig. 59. A sagittal section of an embryo with 56 somites. Embryo killed with 

 Davidoff's fluid. Near the brain the nerve appears composed of loose 

 fibrillae, wliile peripherally it is cellular in appearance. Magnified 360 

 diameters. Reconstructed from five sections. 



Fig. 60. A combination of two parasagittal sections through the left side of an 

 embryo of 16 mm. Protoplasmic processes from the ramus ophth. sup. 

 trig, appear in relation with the anterior projection of the 2d cavity 

 (muse. obi. superior). Magnified 70 diameters. 



Fig. 61. A parasagittal section from the right side of an embrj'o with 51 or 52 

 somites (8 mm.). A well marked fibril passes from the mesocephalic 

 ganglion to van Wijhe's 1st somite. The oculomotorius has not yet 

 appeared. 



