JOURNAL OF MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATES XIII, XIV. 



Illustrating Dr. Milues Marshall's Paper on the 

 " Morphology of the Vertebrate Olfactory Organ." 



Each figure has been drawn from a single section by the aid of a 

 Hartnack camera. The numbers attached indicate, in diameters, the mag- 

 nifying power employed in each case. The majority of the figures are of a 

 semi-diagrammatical nature, the mesoblast being in nearly all cases 

 omitted for the sake of clearness; the outlines are, however, strictly 

 accurate in all cases. Figures 21, 22, 27, and 28 are drawn from sections 

 kindly lent me for the purpose by Mr. Balfour ; the rest are from speci- 

 mens of my own preparation. 



Alphabetical List of Refekences. 

 ah Alimentary canal. aV . Anterior prolongation of alimentary canal. 

 aor. Dorsal aorta. a. r. Anterior root of a spinal nerve. mtcl. Audi- 

 tory vesicle. b. a. Branchial artery. br. 1. First branchial arch. 

 br. 2. Second branchial arch. c. h. cerebral hemisphere. /. b. fore- 

 brain, g. gill. h. 2. Second head-cavity. h . b. Hiudbrain. hi/. 

 Hyoid arch. inf. Infundibulum, I. c. Lachrymal cleft. m. b. 

 Midbrain. Mn. Mandibular arch. m. p. Muscle plate. 3f.v. Maxil- 

 lary arch. u. Notochord. o. c. Optic cup or eye. olf. Olfactory 

 pit. ol. V. Olfactory vesicle or lobe. r. i. Inferior rectus muscle. 

 r. s. Superior rectus muscle. Sch. Schneiderian folds. sp. Spinal 

 cord. tr. Trabecula3 cranii. v. c. Visceral cleft. I. Olfactory 

 nerve. II. Optic nerve. III. Third or oculomotor nerve. V. 

 Trigeminal nerve. V a. Opiithalmic branch of the trigeminal nerve, or 

 ramus ophthalmicus profundus. V 3. Inferior maxillary branch of the 

 trigeminal nerve. VII. Facial nerve. VII a. Ophthalmic branch of 

 the facial nerve, or ramus ophthalmicus superficialis. VIII. Auditory nerve. 

 IX. Glossopharyngeal nerve. X. Vagus or pneumogastric nerve. 



Fig. 1. — Longitudinal and horizontal section through the head of a 

 fifty-four hours' chick embryo, showing early stage in the formation of the 

 olfactory pits, also the visceral clefts with their communication with the 

 exterior. Picric acid, x 35 diameters. 



Fig. 2. — Longitudinal and vertical section through the fore part of the 

 head of a sixty-four hours' chick embryo, showing olfactory nerve and pit. 

 Picric acid, x 27 diam. 



Fig. 3. — Longitudinal and vertical section through the head of a sixty- 

 seven hours' cliick embryo, showing the olfactory pit, the maxillary, man- 

 dibular, hyoideau, and first three branchial arches, with the intervening 

 clefts. Picric acid, x 20 diam. 



Figs. 4—6. — Longitudinal and vertical sections through the head of a 

 ninety-six hours' chick. Picric acid, x 15 diam. 



Fig. 4. — The most superficial of the series ; shows the maxillary, mandi- 

 bular and hyoidean arches, with their intervening clefts, and the trigeminal, 

 facial, and auditory nerves. 



