188 PATTEN. [Vou. II. 
EXPLANATION OF PLATE XII. 
Structure and Development of Eyes If., IV., and VI. 
Fic. 71. Eye VI. as seen in a cross section of the head just after the closure of the 
optic cup. X 430. 
Fic. 72. Same in a little later stage. X 430. 
Fic. 73. Eye VI. of an embryo about ready to hatch. Compare Fig. 9. The 
section is semi-transverse, cutting through the inverted sense organ 6=¢. i. c., and 
the longitudinal vertical axis of eve III. X 430. 
Fic. 74. A similar section through the same eye of a one-day-old larva. X 430. 
Fic. 75. Eye VI. of a full-grown larva, as seen in semi-transverse section. Com- 
pare Fig. 10a. The section passes through the optic nerve of this eye, but does not 
show the tongue of inverted cells. It passes just on the dorsal side of it. X 350. 
Fic. 76. Eyes Il. and IV.=4 and 8, as seen in a longitudinal horizontal section 
of an embryo, some time after the rupture of the embryonic membranes. Compare 
Fig. 9. X 430. 
Fics. 77 AND 78. Eyes II. and IV. of a fully developed larva, as seen in a semi- 
transverse section, nearly parallel with the vertical axis of the first and third eyes. 
X 430. 
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