36 J. T. CUNNINGHAM. 
DESCRIPTION OF PLATES I, I, III, and IV, 
Illustrating Mr. J. T. Cunningham’s Paper “ On the Relations 
of the Yolk to the Gastrula in Teleosteans and in other 
Vertebrate Types.” 
List of more frequent Letters of Reference. 
bl. Blastoderm. e. d. Edge of blastoderm. ep. Epiblast. Ay. Hypoblast. 
gc. Gastrula cavity. me. Mesoblast. xc. Neurenteric canal. xo. Noto- 
chord. pe. Periblast. jv. Perivitelline space. sc. Segmentation cavity or 
blastoccel. ss. Internal limit of dorsal hypoblast on surface of yolk, and 
boundary of segmentation cavity. vm. Vitelline membrane. z. Centre of 
blastoderm in its early condition, and anterior end of embryo. y. Posterior 
end of embryonic rudiment, anterior border of blastopore, point at which 
concrescence occurs. ys. Yolk. z. Posterior border of primitive blastopore 
Figs. 1 to 22 are all drawn from living ova. Figs. 1 to 19 with Zeiss A, Ce. 
9, Abbé’s camera. Figs. 20 to 22 Zeiss A, Ce. 3, without camera. 
PLATE I. 
Fie. 1.—Blastoderm of Gadus eglefinus, L., 74 hours after fertilisation. 
First segmentation furrow. Optical section in plane at right angles to the 
furrow. 
Fic. 2.—Blastoderm of G. eglefinus, | day after fertilisation. Blasto- 
derm forming prominent projection. 
Fic. 3.—Blastoderm of G. eglefinus, 1 day 225 hours. End of period 
of simple segmentation. 
Fic. 4.—Blastoderm of G. eglefinus, 2 days 4 hours. Segmentation 
cavity formed. 
Fic. 5.—Blastoderm of G. eglefinus, 2 days 83 hours. Invagination of 
dorsal hypoblast. 7/. Invaginated layer. 
Fic. 6.—Ovum of G. eglefinus, 2 days 7 hours (exposed to higher 
temperature than ovum from which previous figure was taken). Growth of 
blastoderm over the yolk. 
Fic. 7.—Ovum of G. eglefinus, 2 days 223 hours. The edge of the 
blastoderm has passed the equator of the yolk. oc. Cerebral part of eye. 
Fic. 8.—Ovum of G. eglefinus, 3 days 22 hours. Segmentation cavity 
not visible in optical section. az. Otocyst. dr. Branchial slits. dc. Intes-. 
tinal cavity. dd. Liver. oc. Hye. 
Fic. 9.—Ovum of G. eglefinus, 5 days. Final closure of blastopore. 
ee 
