PAKACOROTOPA AKKILMANl (waKHKN). 341 



'Jlie iiieso- and metatlioracic ganglia arc in close, wide cojitact 

 with each other. 'J'lie abdominal ganglionic mass is in direct 

 contact Avith the metatlioracic ganglion. This mass shows 

 much more clearly than in Paracorotoca its compound 

 nature, the anterior portion of the mass being almost moni- 

 liform. There are 6 obvious ganglia and an end-piece. It 

 is not possible to determine by mere inspection whether the 

 terminal portion consists of one or two ganglia. Judging 

 from the number of ganglia (8) in the supposed larva of 

 Paracorotoca this portion is composed of two fused ganglia. 

 The abdominal ganglionic mass is not di-awn so far forward 

 as in Paracorotoca, since it extends backwards as far as 

 the 3rd or the bes'innino- of the 4th abdominal seg-ment. 



Compound Eye. — Externally the eye appears normal in 

 character (PI. XVI, fig. 7) ; there is considerable development 

 of pigment, and the facettes, which are approximately 120 in 

 number, although large, are less so tlian in Termitomimus, 

 Internally, however, the organ is abnormal, and the omma- 

 tidial region is shallow, so that in vertical section the eye is 

 distinctly flat. The flat eye is largely cut off from the inside 

 of the head by a layer of chitin continuous with the general 

 exoskeleton (PI. XYII, figs. 39 and 40, i. c), and the liuge 

 mandibular adductor muscles {m. m.) extend slightly on to 

 this chitinous layer. The optic plate (op. -p.) is degenei-ate 

 in character, and in the specimen cut into serial sections it 

 had become entii-ely disconnected from the optic ganglion of 

 the brain (fig. 39, oj). g). 



The ommatidial elements are remarkably degenerate : there 

 is some remnant of the cone-layer of cells (figs. 41, d. c c.) 

 interspersed with coarse iris pigment-cells (/. j). c), but the 

 layer is almost of the nature of a plasmodium with vacuoles 

 at the pei-iphery. The rhabdome or i-etinal cells are exces- 

 sively degenerate {d. rh. c.) and are attached to the degenerate 

 optic plate [d. op. i).). There is a certain amount of coarse- 

 retinal pigment (?-. p. c). The general region which should 

 be occupied by the rods is mostly cavity irregularly traversed 

 by protoplasmic strands carrying pigment-cells and also. 



