DIVIDED EYES OF CERTAIN INSECTS 475 



the rhabdome is seen to be star-shaped with the " secondary 

 rods " beginning to develop between the boundaries of the 

 retinular cells. Fig. 19 shows the structure of the turban eye 

 elements of an old sub-imago of C. caltfornica — i. e. y just 

 before time for the adult to issue. The cornea is still thin, but 

 the secondary pigment cells have pushed it up a little and the 

 distal ends of these cells may be seen overlapping the bases of 

 the cones between c and en (Fig. 19). The retinula is now more 

 nearly pinched into two. I was unable however, to demonstrate 

 the presence of any nuclei in this retinula of the sub-imago 

 below the constriction (d, Fig. 19) as might perhaps be expected. 

 Otherwise the preparation for the separation of the distal and 

 proximal retinulas and for the formation of the hypodermal 

 space seems complete in this stage of the development. 



It is wonderful to see the rapid enlargement of the turban 

 eyes as the adult issues from its sub-imago stage. Sub-imagoes 

 issue from the nymphs in less than 3 seconds. The process for 

 the adults is longer — 40 to 60 seconds — but the head enlarges 

 immediately upon breaking through the chitin, and the turban 

 eyes expand almost to bursting with a liquid. When photo- 

 graphs 24 and 26 of the adult eye are compared with 23 and 25 

 of the sub-imago or drawing 16, A, with drawing 19, it is clear 

 what happened to permit the enlargement. The secondary 

 pigment cells which overlapped the bases of the cones have 

 straightened up. The cornea has been lifted to permit this and 

 thus the hypodermal space is formed — being bounded by the 

 cornea, the cone and the surrounding secondary pigment cells. 

 The liquid contents of this space and the secondary pigment 

 cells together, undoubtedly secrete the thicker corneal lens of 

 the adult eye. That is to say, the hypodermal space is anal- 

 ogous to a cell in this eye, but it is in no sense homologous to 

 a cell as is shown by its origin. Furthermore, the space between 

 the distal and proximal retinulae is to be directly associated with 

 the rapid expansion of the eye of the issuing adult. The narrow 

 connecting portion of the retinula of the old sub-imago (Fig. 19) 

 has been stretched to form the connecting strands of the adult. 

 It must be observed here also that the proximal retinulse out- 

 number the distal in the old sub-imago and in the adult. The 



