PINEAL AND PITUITARY BODIES OF THE BRAIN. 25 
EXPLANATION OF THE PLATES. 
Norr.—Figures 3 and 4 in Plate II. are intended only as diagrams to aid the 
reader in following the speculations in regard to the subneural gland and 
dorsal tuberele given in the text, and must not be considered as representing 
in detail the author’s views in regard to the probable condition of the 
hypothetical ancestral Chordata. 
LETTERING.—~., pineal gland; h., pituitary body; 7., retina; l., lens; ., nerve; 
C(n)., C(v)., C(e)., central cavity in pineal, vertebrate and invertebrate 
eye; d.t., dorsal tubercle; d., duct; s.g., subneural gland; g., nerve ganglion; 
ch., notochord ; x.c., neural canal; s¢., stomodeum; pr., proctodeum ; 
neph., nephridia; @.n., anterior nephridium; ¢., Thalamencephalon. 
PuATE I. 
Fig. 1. Diagrammatic vertical longitudinal median section 
of the vertebrate brain, showing the relations of 
the Pineal gland (e.) and Pituitary body (h.) to 
the Thalamencephalon (¢.) (partly after Huxley, 
partly after Wiedersheim). 
Fig. 2. Diagrammatic section of the vertebrate paired eye. 
Fig. 3. Diagrammatic section of the pineal eye of Hatteria 
(after Spencer). 
Fig. 4. Diagrammatic section of an invertebrate eye. 
Fig. 5. Diagram of the eye of a larval Tunicate (after 
Kupffer). 
Phare Ef. 
Fig. 1. Diagram showing the relations of the dorsal 
tubercle (d.t.), subneural gland (s.g.), and 
ganglion (g.), in an Ascidian. 
Fig. 2. The dorsal tubercle, &c. of Ascidia mentula from 
the ventral surface (after Julin). 
Fig. 3. Diagrammatic representation of the anterior end 
of hypothetical Proto-Chordate, showing renal 
organs (nephridia) opening on the left side on 
the surface of the body, and on the right into 
the peribranchial involution. 
Fig. 4. Diagrammatic representation of hypothetical Proto- 
Chordate from the left side. 
