PLATE Ii. 
Fic. 10. Outline drawing of an embryo of the third operative stage (IX). 
x 6% diameters. 
Fig. 11. Section through eye region of an embryo of the same stage (IX) 
as above, showing the lens-plate thickening of the inner layer of ectoderm. 
x 45 diameters. 
Fic. 12. Experiment IX,,. Section through right abortive lens of an 
embryo 8 days after the removal of the optic vesicle. There is an indication 
of the medial-pole, but no definite lens-fibers are present. The lens measures 
140 » in diameter, being much smaller than the normal one below. X 180 
diameters. 
Fic. 13. Experiment IX,,. Section through left normal lens of above 
embryo after 8 days. Developed from lens-plate thickening of ectoderm 
(IX) to lens 170 in diameter. X 180 diameters. 
Fic. 14. Experiment IX,. Section through right abortive lens, showing 
degenerated ectodermal cells apparently, and no well defined medial-pole. 
The embryo was killed 14 days after the removal of the optic vesicle. X 180 
diameters. 
Fic. 15. Outline drawing of fourth operative stage (X), showing no 
division of the gill mass. X 614 diameters. 
Fic. 16. Section through eye region of an embryo of the above stage (X), 
showing a well-defined lens-bud. > 45 diameters. 
Fie. 17. Experiment X,,. Section through right lens 14 days after the 
complete extirpation of the optic cup. The medial pole has disappeared, and 
only a few lens-fibers indicate its former position. The lens is small, meas- 
uring only about 100 uw, while the normal one is about 160 yw in diameter. 
x 180 diameters. 
Fie. 18. Experiment X,,. Section through right lens of an embryo killed 
7 days after the operation. The lack of influence of the optic cup -has re- 
sulted in the retardation in growth and differentiation of the lens. x 180 
diameters. 
Fic. 19. Experiment X.,. Section through the left normal lens of the 
above embryo. > 180 diameters. 
