JOURNAL OF MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATE XXVII, 



Illustrating Prof. Marshall's and Mr. Spencer's Paper on 

 " The Cranial Nerves of Scylliura.'" 



All the figures are taken from sections of ScyUium 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, and IG, 

 are of a diagrammatic nature, each being constructed by combining a 

 number of sections fi'om the same embryo; in these, as in tlie other 

 figures, the outlines were in all cases drawn by means of a Hartnack camera. 



The numbers attached indicate, in diameters, the magnifying power 

 employed. 



Alphabetical List of References. 



aud., auditory vesicle ; Br. 1, first branciiial arch ; c. g., ciliary ganglion ; 

 cr., cerebellum ; h. b., hind-brain; Z/y., hyoid arch; ?>?/., in fnndibulum ; 

 /., lens ; m., muscle ; m. b., nnd-braiu ; m. c, mucous canal ; Mn., mandi- 

 bular arch ; «., notochord ; N., nerve from ciliary ganglion to fore part of 

 head, forms the distal portion of the ramus ophthalmicus profundus ; 

 N. c, communicating branch b;tween third aud fifth nerves, forms 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 invo- 

 lution from mouth; r. e., rectus externus ; r. i., rectus inferior ; r. int., 

 rectus internus ; r. s., rectus superior; spr., spiracle, ^ hyomandibular 

 cleft ; 1, first head cavity ; 2, second head cavity ; 3, third head cavity ; 

 I, olfactory nerve ; ii, optic nerve ; iil, third, or oculomotor nerve ; 

 III b, branch of third nerve to rectus superior ; iii c, branch of third nerve 

 to obliquus inferior; lll^, ? secondary root of ill; III y, anterior roots 

 of III ; IV, fourth nerve, or patheticus ; v, fil'tli, or trigeminal nerve ; 

 \ a, ophthalmic branch of fifth nerve; v^, maxillary branch of fiftli ; vc, 

 mandibular branch of fifth ; va, primary dorsal root of fifth ; v /3, secon- 

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

 abducens nerve ; vii, seventh, or facial nerve ; vii a, ophthalmic branch 

 of seventh nerve ; vii b, mandibular branch of seventh ; wxpa, palatine 

 division of mandibular branch ; vii sp, spiracular division of mandibular 

 branch; vii <?, hyoidean branch of seventh ; viicl, ramus mandi'mlaris 

 externus, or branch of Jiyoidean into mandibular arch ; vii c 2, rarnus man- 

 dibularis interims, or terminal branch of hyoidean to walls of third head 

 cavity ; vii d, buccal branch of seventh ; vii a, original dorsal root of 

 seventh; vii/3, secondary root; viii, eighth, or auditory nerve; ix, 

 ninth, or glossopharyngeal nerve; ix «, ramus dorsalis ol ninth nerve; 

 IX ^, hyoidean branch of ninth; ixc, branch of niutli to first branchial 

 arch; x, tenth, or pneumogastric nerve; X b, anterior branch of tenth 

 nerve in first branchial arch. 



