'342 ERNEST WARREN. 



loose granules of pigment. From the fact that the connection 

 between the optic plate and the optic ganglion of the brain 

 has disappeared it is clear that the insect must be blind; 

 but even if a connective does sometimes persist in certain 

 individuals, yet the condition of the ommatidial elements is 

 such that the eye would be practically useless. 



The peculiar condition of some of the cortex cells of the 

 optic ganglion (PI. XIX, figs. 49, 50, 51, d. c, d. n. c.) is very 

 possibly associated with the degeneration of the eye itself. 



The compound eye is being gradually cut off from the 

 inside of the head by the ingrowth of the exoskeleton from 

 around the periphery. In fig. 40, i. cic, we see that a portion 

 of the optic plate has been under-cut by this cliitin layer 

 secreted by an ingrowth of the general hypodermis (ec.) . If we 

 imao-ine this insTOwing- of cuticle to continue a little farther 

 the eye would be completely cut off from the cavity of the 

 head and would fall away and leave a groove at the side of 

 the head. Such a groove, representing the compound eye, is 

 seen in certain small subterranean beetles, and it is suggested 

 that this eye-less condition has gradually arisen through 

 «uch a stage as is now present in Paracorotoca. 



The condition of the eye in Termitomimus would seem to 

 be essentially similar. The ommatidial elements, especially 

 the rhabdome cells, are deficient, and the eye is largely cut 

 off from the inside of the head by a remarkably strong chitin 

 layer. The optic plate, however, still retains some connection 

 Avith the optic ganglion of the brain. 



In Termitodiscus splendidens we find an analogous 

 condition. The ommatidial elements are densely packed 

 with pigment, and it is necessai-y to bleach the sections 

 before any cellular structure can be observed. The optic 

 plate (PI. XYII, fig. 42, oj7.) is very thin and is only connected 

 very inefficiently with the outer edge of the optic ganglion 

 {op. g.). The eye is so greatly cut off from the head by 

 ingrowing cuticle [i. c.) that there is very little space for an 

 optic plate, and the whole structure appears to have been 

 ■orientated forwards out of its proper position with reference 



