100 



THE COCKROACH : 



a triangle on the forehead. The white fenestrsc, which in the 

 Cockroach lie internal to the antennary sockets, may represent 

 two simple eyes which have lost their dioptric apparatus. In 

 many larvae only simple eyes are found, and the compound eye 

 is restricted to the adult form ; in larval Cockroaches, however, 

 the compound eye is large and functional. 



Co.F 



Cr- 



Fig. 51. One element of the Compound Eye of the Cockroach, X 700. Co. F. 

 corneal facets; Cr, crystalline cones; Em, nerve-rod (rhabdom); HI, retinula 

 of protoplasmic fibrils. To the right are transverse sections at various levels. 

 Copied from Grenadier. 



Each facet of the compound eye is the outermost element of a 

 series of parts, some dioptric and some sensory, which forms 

 one of a mass of radiating] rods or fibres. The facets are 



