1883.] NATURAL SCIENCES OF PHILADELPHIA. 185 



EXPLANATION OF PLATE VIII. 

 Illustrating the Brains op Amphioma and Menopoma, 



Lettering and Abbreviations. 



Eh. — Rhinencephalon ; Pr. and Pro. c. — Prosencephalon and Procoelia ; Di., 

 Bi. t. and Di. c. — Diencephalon, Diatela (roof of Diencephalon), and 

 Diaccelia ; Me. and Me. c. —Mesencephalon and Mesocoelia ; Ep. and 

 Ep. c. — Epencephalon and Epicoelia ; Met. — Metencephalon. 



Tc. — Tuber cinereura ; ch. — optic chiasma ; pt. — pituitary body ; p w. — pineal 

 gland; era.— infundibulum ; c/to.— choroid plexus; cr.— crura cerebri ; 

 p. cm. — prsecommissura (anterior commissure); i^.— optic thalamus. 



I, — Optic; II. — Olfactory ; III— Oculo-Motor ; V.— Trigeminis ; VL — 

 Abducens; VIL — Facial; VIII. -Auditory ; IX, X, XL— Vagus 

 Group. N. B. —The identification of yie nerves was by noting their 

 origin ; the distribution of the nerves has not been -worked out. 



Special References in Figures. 



Figures A-D, twice natural size. Figs. H and 1-13, eight times natural 

 size. 



Figure A. Dorsal view of the brain of AmpMuma. 



Figure B. Ventral view of the same. 



Figure C. Dorsal view of the brain of Menopoma. 



Figure D. Lateral view of the same. Dit. corresponds to vertical line 

 7, tig. H. 



Figure E. Enlarged view (about 30 diameters) of a longitudinal section 

 of the cerebellum and a portion of the optic lobe, taken at one side 

 of the median line. The valvula, v, is broader in the median line ; 

 d, white, e, gray portion of Mesencephalon ; a, fine longitudinal fibres ; 

 b, transverse band of fibres ; c, cortical layer of cells. 



Figure F. Transverse section of the cerebellum, lettering as in fig. E. 



Figure G. a, large, b, small cells found in crura cerebri (30 diameters). 



Figure H. Longitudinal section of the brain of Ainfhiuma, taken to the 

 left of the median line. Vertical lines, 1 to 13, correspond to trans- 

 verse sections represented by figs. 1 to 13. Black line represents the 

 pia mater ; the roof of the metacoelia (fourth ventricle) is omitted in 

 the drawing. 



Figure 1. Vertical transverse section through cerebellum, showing it as 

 a transverse band passing beneath Mesencephalon. 



Figure 2. Ditto through pituitary body and infundibulum, showing 

 crura cerebri and optic lobe unpaired. 



Figure 3. Sliowing sides of infundibulum thickening into tuber cinereum. 



Figure 4. Through posterior portion of the Diencephalon. 



Figure 5. Through the median portion of the Diencephalon. 



Figure 6. Slightly anterior to fig. 5. y, a constriction of the upper por- 

 tion of the diaccelia. 

 IS 



