470 



MORGAN. 



EXPLANATION OF PLATE XXIV. 



Zeiss, 2 AA, Abbe. Camera, x 85. 

 Zeiss, 2 D, Abbe. " x 370. 



Figs. 13-24. Ctenolabrus. 



Fig. 13, A. Section through blastoderm, X.2D, at 9 a.m. 



Fig. 13, .5". " " germ-ring of same, X 370. 



Fig. 13, C. " " center of blastoderm, X 370. 



Fig. 14, A. Longitudinal section through blastoderm, at 11 A.M., X85. 



Fig. 14, B. Cross-section same, X8s. 



Fig. 14, C. Section through germ-ring, X 370 (14, A). 



Fig. 14, D. " " side of germ-ring, X 370 (14, B). 



Fig. 14, .£■. " " center embryonic shield, X 370. 



Fig. 15, A. Longitudinal section through blastoderm, at i.io P.M., X85. 



Fig. 15, B. Cross-section same, X85. 



Fig. 15, C. Section through germ-ring, X 370 (15, A). 



Fig. 15, Z?. " " side of germ-ring, X 370 (15, j?). 



Fig. 16, A. Longitudinal section through blastoderm, at 3 p.m., XS5. 



Fig. 16, B. Section through germ-ring, X 370 (16, A). 



Fig. 16, C. " " side of germ-ring, X 370. 



Fig. 17, A. Cross-section through germ-ring and yolk-exposure, at 5.30 

 P.M., X85. 



Fig. 17, B. Section of germ-ring at posterior end, X 370. 



Fig. 17, C. " " " " side, X370. 



Fig. 18, A. Longitudinal section ofembryo and germ-ring, X 370, at 7.05 p.m. 



Fig. 18, B. Cross-section of germ-ring, X 370, at 7.05 p.m. 



Fig. 19, A, B. Surface view of cells of extra-embryonic region {A) and of em- 

 bryonic region {B) (see text), at 6.05 P.M., 7_^ hrs. old, X 370. 



Fig. 20, A, B. Ditto, at 8.30 p.m., X 370. 



Fig. 21, A, B. Ditto, at 9.30 P.M., X 370. 



Fig. 22, A, B. Ditto, at 2.10 p.m. (another lot), X 370. 



Fig. 23, A-D. A, B, ditto, at 3 p.m. C, surface cells at posterior end of 

 embryo. Z>, surface-cells of germ-ring, X 370. 



Fig. 24. Surface cells of extra-embryonic region, at 7.05 p.m., X 370. 

 Figs. 25-31. Fundulus. 



Fig. 25, A-D. A, 2-cell stage. Egg of Fundulus. Unequal division. 

 Smaller cell removed. Larger cell divided. B, 2-cell 

 stage {=}4. 4-cell). C, 4-cell stage {=^2 8-cell). D, 8-cell 

 stage {=% i6-cell). 



Fig. 26. 8-cell stage (=^ i6-cell). Taken from an egg that divided nor- 

 mally into two equal blastomeres, of which one was removed. 



Fig. 27. 4-cell stage of normal egg with very unequal cleavage. Formed 

 normal embryo. 



Fig. 28. Embryo Fundulus. Developed from one of the first two blastomeres. 



Fig. 29. Embryo Fundulus. Normal. Same stage as last. 



Fig. 30, A~C. A, normal embryo Fundulus, side view, optical section. 

 B and C, embryos developed from one of first two blasto- 

 meres. 



Fig. 31, A-C. A, head of normal embryo. B and C, head of embryos de- 

 veloped from one of first two blastomeres. 



