120 PROP. MARSHALL AND MR. SPENCER. 



DESCRIPTION OF PLATES V— VI. 



All the figures are taken from sections of Scyllium embryos. 

 Figures 1, 2, 3, 4, 5, 6, 8, and 13, were drawn from single sections. 

 Figures 7 and 9 each represent two sections, the right hand half of 

 the figure being in both cases taken from a section a short distance 

 posterior to that represented in the left hand half. The remaining 

 figures, viz. 10, 11, 12, 14, 15, 16, and 17, are of a diagrammatic nature, 

 each being constructed by combining a number of sections from the 

 same embryo ; in these, as in the other figures, the outlines were 

 drawn by means of a Hartnack camera. 



The numbers attached indicate, in diameters, the magnifying power 

 employed. 



Alp>habetical List of References, 

 aud., auditory vesicle ; Br. 1, first branchial arch j e.g., ciliary 

 ganglion ; cr., cerebellum ; h.b., hind-brain ; Ey., hyoid arch ; inf., 

 infundibulum ; I., lens; m., muscle; m.b., mid-brain; m.c, mucous 

 canal ; Mn., mandibular arch ; n., notochord ; N~., nerve from ciliary 

 ganglion to fore part of head, forming the distal portion of the ramus 

 ophthalmicus profundus ; N.c, communicating branch between third 

 and fifth nerves, forming the proximal part of the ramus ophthalmicus 

 profundus; N.c'., communicating branch between fifth and seventh 

 nerves; o.c, optic cup; o.i, obliquus inferior; olf. } olfactory pit; 

 o.s., obliquus superior; pit., pituitary involution from mouth; r.e., 

 rectus externus ; r.i., rectus inferior; r.int., rectus internus; r.s., 

 rectus superior; spr., spiracle, or hyomandibular cleft; 1, first head 

 cavity ; 2, second head cavity ; 3, third head cavity ; i, olfactory 

 nerve ; n, optic nerve ; in, third, or oculomotor nerve ; in b, branch 

 of third nerve to rectus superior ; hi c, branch of third nerve to 

 obliquus inferior ; in /3, 1 secondary root of hi ; in y, anterior roots 

 of in ; iv, fourth nerve, or patheticus ; v, fifth, or trigeminal nerve ; 

 v a, ophthalmic branch of fifth nerve ; v b, maxillary branch of fifth ; 

 v c, mandibular branch of fifth ; v a, primary dorsal root of fifth ; v /3, 

 secondary root of fifth ; v y, anterior, or tertiary roots of fifth ; vi, 

 sixth, or abducens nerve ; vn, seventh, or facial nerve ; vn a, oph- 

 thalmic branch of seventh nerve ; vn b, mandibular branch of seventh ; 

 vn pa, palatine division of mandibular branch ; vn sp, spiracular 



