RELATIONS OF YOLK TO GASTRULA IN TELEOSTEANS. 37 
PLATE II. 
Fic. 10.—Ovum of G. eglefinus, 6 days 21 hours. Intestinal tube 
completely separated from yolk. 
Fig. 11.—Blastoderm of G. morrhua, L., 1 day 3 hours. Advanced 
stage of segmentation. 
Fie. 12.—Ovum of G. morrhua, same stage as in last figure, showing 
continuity of blastoderm with yolk. Origin of periblast. 
Fic. 13.—Blastoderm of G. morrhua, 1 day 163 hours. End of period 
of simple segmentation. ye. Periblast. 
Fic. 14.—Blastoderm of G. morrhua, 1 day 21 hours. Segmentation 
cavity formed. 
Fig. 15.—Ovum of G. morrhua, same stage as in last figure. Superficial 
view of blastoderm. 
Fre. 16.—Blastoderm of G. morrhua, 2 days 1 hour. Invagination of 
dorsal hypoblast. 
Fie. 17.—Ovum of G. morrhua, same stage as in last figure. Superficial 
view of blastoderm. 
Fic. 18.—Ovum of G. merlangus, L., 3 days 17 hours. Blastopore 
nearly closed. &.v. Kupffer’s vesicle. 
PLATE III. 
Fic. 19.—Ovum of Trigla gurnardus, 22 hours. 
Fic. 20.—Ovum of Clupea harengus, L., 1 day 6 hours. (Temp. about 
18°C.) Blastoderm enveloping more than half the yolk. 
Fie. 21.—Ovum of Cl. harengus, 1 day 10 hours. Yolk almost enclosed. 
Fic. 22.—Ovum of Cl. harengus, 1 day 143 hours. Closure of the 
blastopore. 
Fic. 23.—Diagram representing pelagic Teleostean ovum in perspective, 
to illustrate the process of concrescence of the lip of the blastopore. 
PLATE IV. 
Fic. 24.—Diagram of section of pelagic Teleostean ovum at the completion 
of simple invagination, before the growth of the blastoderm over the yolk. 
Fie. 25.—Diagram of section of same ovum at a later stage, when the 
blastoderm has covered more than half the yolk. 
Fie. 26.—Diagram of section of same ovum, when the yolk is almost 
covered by the blastoderm. 
