ATA BERTRAM H. WATERS. 
25. Van Wisue.— Ueber die Mesodermsegmente und die Kntwickelung 
der Nerven des Selachier Kopfes,” ‘ Natuurk Verhandelingen 
Koninkl. Akademie,’ Amsterdam, Deel xxii, 1882 (Sept.). 
26. Von Barr.—‘ Entwickelungsgeschichte der Thiere,’ Th. 1, p. 64. 
27. Warers.—* Additional Points on the Primitive Segmentation of the 
Vertebrate Brain,” ‘Zoologischer Anzeiger,’ No. 362, 1891. 
28. WiepeRsHuIm.—‘ Comparative Anatomy of Vertebrates.’ 
29. Witprr.—“ Brain,” ‘Reference Handbook of the Medical Sciences,’ 
vol. viii, p. 8. 
EXPLANATION OF PLATE XXVIII, 
Illustrating Mr. Bertram H. Waters’s paper ‘“‘On the Primi- 
tive Segmentation of the Vertebrate Brain.” 
Index Letters. 
I. a., 11. n., UI. n., &¢. First, second, third, &., cranial nerves. ap. Apex 
aud internal edge of neuromere. ¢.c. Thalamocele. m.c. Mesoceele. o/. 0. 
Olfactory vesicle. op. dw. Optic lumen. c.s. Corpora striata. az. v. Auditory 
vesicle. c. m. White cortical substance. p.c. Posterior commissure. spt. 
Neural septa. N.1, V2, V3, &. First, second, third, &c., neuromeres. 
epi. Epiblast. Zp. Epiphysis. 4¢2 V. Fourth ventricle. F. B. Fore-brain. 
M. B. Mid-brain. H. B. Hind brain. 
All figures of sections have been drawn with the Abbey camera lucida and 
a Zeiss’s microscope, a Zeiss’s ocular No. 2 and objective A being used. 
Fre. 1.—Longitudinal horizontal section of Gadus morrhua, six days’ 
incubation, showing unsegmented fore- and mid-brain region, and hind brain 
neuromeres. 
Fic. 2,.—Same at ten days, showing olfactory region and nerve (o/. v.), the 
thalamocceli and region of optic lumen (op. /w.), posterior commissure (p. ¢.), 
the region of the third and fourth neuromeres, and probable place of origin 
of fourth nerve. 
Fic. 3.—Same at ten days, showing olfactory region, and diagrammatically 
representing the third, fourth, and fifth neuromeres. 
Fic. 4.—Same at eight days, showing thalamoccele (¢. ¢.), and third, fourth, 
and fifth neuromeres with radial cell arrangement. 
