DESCRIPTION OP PLATES V AND Yl.— Continued. 



ciliary gaiiglioa with tlie two branches of the third nerve arising from 

 it, and the communicating braucli between the third and fifth nerves. 

 X 25. 

 ElGS. 5 and 6. — Longitudinal and vertical sections through the head of 

 an embryo of stage L. 



Fig. 5 shows the whole length of the second head cavity ; also the 

 third head cavity, and the fifth nerve, with the roots of its ophthalmic 

 and communicating branches, x 20. 



Fig. 6 shows the filth nerve with its anterior non-ganglionic roots, 

 and its posterior ganglionic root ; also the root of the ophthalmic 

 branch of the fifth, x 25. 

 Figs. 7 to 14. — Longitudinal and vertical sections through the head of an 

 embryo of stage l. x 25. 



Fig. 7, the most superficial of the series, shows the second head- 

 cavity, and parts of the trigeminal, facial, and auditory nerves. 



Fig. 8 shows the second head cavity, and the wall of the first and 

 third ; also the filth, seventh, and auditory nerves. 



Fig. 9 shows the three head cavities, the fifth nerve with the root of 

 its ophthalmic branch, the facial, and auditory nerves. 



Fig. 10 shows the three head cavities, the ciliary ganglion "with the 

 roots of the two branches of the third nerve, the trigeminal with the 

 posterior part of the communicating branch. 



Fig. 11 shows the three head cavities, the ciliary ganglion with the 

 anterior end of the communicating branch, the trigeminal nerve with its 

 anterior and posterior I'oots and the root of the ophthalmic branch, the 

 auditory nerve, and the olfactory nerve. 



Fig. 12. shows the first and third cavities, and a part of the inner 

 wall of the second ; also the third and olfactory nerves, and the pineal 

 body. 



Fig. 13, the median section of the series, shows the notochord end- 

 ing against the median portion of the first head cavity, also the infundi- 

 bulum and pituitary involution. 



Fig. 14, taken from the opposite side of the body to the preceding 

 sections ; shows the first head cavity, and the root and greater part of 

 the length of the third nerve. 

 Figs. 15 to 20. — Longitudinal and vertical sections through the head of a 

 Scyllium embryo of stage m. x 20. 



Fig. 15, the most superficial of the series, shows the olfactory nerve 

 and pit, the anterior branch of the third, and the palatine and hyoidean 

 branches of the seventh nerve ; also the spiracular cleft with its branchite. 



Fig. 16 shows, in addition to the parts seen in the preceding figure, 

 the ophthalmic branch of the seventh, the maxillary and mandibular 

 branches of the fifth, and the lower part of the mandibular head cavity. 



Fig. 17 shows the same parts as Fig. 16, but at a somewhat deeper 

 level. 



Fig. 18 shows the olfactory nerve and pit, the anterior branch of the 

 third nerve, the mandibular branch and main stem of the fifth, and the 

 ophthalmic branch and main stem of the seventh ; also the rectus externus 

 muscle. 



Fig, 19 shows the first cavity flattened out and embracing the eyeball, 

 anterior and posterior branches of third nerve, ciliary ganglion, ophthal- 

 mic and communicating branches of fifth, ophthalmic branch of seventh, 

 rectus inferior and obliquus inferior ; also terminal portion of mandibular 

 head cavity, with its walls converted into muscles. 



Fig. 20, taken from the opposite side of the body, shows ciliary 

 ganglion, and the two branches uf the third nerve arising from it ; com- 

 municating branch of the fifth, with its branch to the obliqmts superior ; 



