190 PATTEN. [VoL. Il. 
EXPLANATION OF PLATE XIII. 
Fic. 79. Eye I. as seen in a semi-transverse section of an embryo just after the 
rupture of the embryonic membranes. Compare Figs. 8 and 16. X 520. 
Fic. 80. The same, after the sensory area is differentiated into the vertical and 
horizontal retinas. 
Fic. 81. The same, from an embryo some time before hatching. 
Fic. 82. Transverse section of the sensory area of Eye I. in the stage shown in 
Fig. 14. X 560. 
Fic. 83. Same, of Eye III. in a later stage. The median furrow has disappeared 
and the invagination of the sensory area has commenced. X 560. 
Fic. 84. Cross section of the vertical retina of Eye I. in the full-grown larva. 
X 430. 
Fic. 85. Eye I. as seen in a tangential section of the side of the head. The sec- 
tion is at right angles, and from an eye in the same stage, to that shown in Fig. 8o. 
X 415. 
Fic. 86. Section, in same direction as the preceding, of Eye I. just before hatch- 
ing. X 260. 
Fic. 87. Transverse section of Eye I. in same stage as shown in Fig. 79. The 
section passes through the large nucleus of the horizontal retina. 
Fic. 88. Section similar to the preceding one, through the vertical retina of the 
same eye. X 430. 
Fic. 89. Horizontal section through the horizontal retina of Eye I. during a little 
earlier stage than that shown in Fig. 85. X 430. 
Fic. 90. Eye III. as seen in a tangential section of the head of a full-grown larva; 
partly depigmented. X 240. 
Fic. 91, Eye I, in same section as the preceding. X 240. 
