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THE AMERICAN NATURALIST. [Vol. XXXVII. 



circular in outline, the diameter from the anterior to the posterior 

 margin being slightly greater than that from the dorsal to the 

 ventral margin. 



The eyes appear light green in the centre with a peripheral 

 band of reddish brown. 



The corneal cuticle. — The corneal cuticle, a transparent con- 

 tinuation of the body cuticle, is divided into facets which are, 

 with a few exceptions on the periphery of the eye, uniformly 

 hexagonal and of the same size (Fig. 3 a). Each eye contains 

 between 450 and 525 facets. The facets have a maximum width 

 of 23I microns between their parallel faces and 25% microns 

 between opposite angles (Fig. 3 a). 



The corneal cuticle differs somewhat in thickness in different 

 individuals, reaching a maximum in those insects about ready to 

 moult. The line of separation between the old and the newly 

 formed cuticle is very distinct. This, in individuals -about to 

 moult is caused by the fact that the former is more deeply 

 staining than the latter (Fig. 3). The maximum thickness of 

 the cuticle at the centre of each facet is nine and one third 



The corneal hypodermis.— Proximad of the corneal cuticle 

 and separating it from the cone-cells is the corneal hypodermis 

 — a layer of well differentiated cells and one of considerable 

 thickness (Fig. 3). There are two hypodermal cells beneath 

 each facet. The distal surface of each pair of hypodermal cells 

 is flat and hexagonal in outline (Fig. 3 b). This outline coin- 

 cides exactly with that of the corresponding facet. 



Extending across the distal surface of each pair of cells and 

 perpendicular to two opposite sides of their hexagonal outline is 

 a straight deeply staining line which marks the separation of the 

 two cells. (Fig. 3 b). These lines are not all strictly parallel. 



Proximad, the hypodermal cells become considerably smaller, 

 having a width at their proximal end equal to that of the under- 

 lying cone which is 6 microns less than the width of the distal 

 surface of the hypodermal cells. The proximal surface of each 

 pair of cells is concave. (Fig. 3.) 



The nuclei of the hypodermal cells are large and deeply stain- 

 ing. In transverse sections through the distal end of these cells 



