PLATE I. 
Fig 1. Outline of an early stage of amblystoma, just after closure of the 
neural folds. First operative stage (VII). X 6% diameters. 
Fig. 2. Section through eye region of an embryo of the same stage as 
above (VII). Optic vesicle in contact with the ectoderm, which shows no 
signs of lens formation. X-°45 diameters. 
Fie. 3. Experiment VII,,.2 Section through small abortive lens-like struc- 
ture in the ectoderm in normal position for the lens. The embryo was 
killed 30 days after the complete extirpation of the optic vesicle. x 180 
diameters. 
Fig. 4. Outline drawing of an embryo of the second operative stage (VIII), 
showing first appearance of tail-bud. Xx 6% diameters. 
Fic. 5. Section through eye region of an embryo of the same stage (VIII) 
as above. The ectoderm shows some changes, as the beginning of the thick- 
ening of its inner layer for lens formation. X 45 diameters. 
Fie. 6. Experiment VIII,,. Section through normal lens after 6 days. 
xX 180 diameters. 
Fic. 7. Experiment VIII,,. Section through right lens of above embryo 
6 days after the complete extirpation of the optic vesicle, showing abnormal 
development as a resultant effect. At the time of the operation the lens- 
plate was visible as a mere thickening of the ectoderm. > 180 diameters. 
Fie. 8. Experiment VIII, Section through the right lens of an embryo 
killed 30 days after removal of the optic vesicle. The lens shows marked 
retardation and lack of differentiation, and the lens-fibers are much degen- 
erated. It measures about 110 u in diameter, being much smaller than the 
normal lens. X 180 diameters. 
Fie. 9. Experiment VIII.,,. Section through normal left lens of above 
embryo after 30 days. 260 »in diameter. (Contrast Fig. 8.) X 180 diame- 
ters. 
The Roman numerals indicate the operative stage. 
