628 William Patten 



become bevelled, thus giving to a cross section an octagonal outline 

 (figs. 79 and 80). Stili farther inward, the comers are rounded, giving 

 rise to a tube, decreasing in diameter towards the inner end until it is 

 reduced to a slender, hollow stalk — the style — which, enlarging 

 rapidly, becomes transformed into a solid, pyramidal thiekening — the 

 pedicel ; the latter rests upon the basai membrane by a delicate stalk, 

 divided at its inner extremity into three legs, formed by the diverg- 

 ing ends of the four retinophorae , tv/o of which bave united. The 

 rounded, outer ends of the retinophorae are provided with peculiar, 

 protoplasmic thickenings in which the nuclei are situated (fìg. 69 

 n.rf). They may be seen in cross sections, but more easily in 

 macerated pieces of cornea to which the ends of the retinophorae, 

 with their nuclei, remain attached. The latter are coarsely granular, 

 ovai bodies in which there are vacuoles, often so large as to trans- 

 form the nucleus into a mere shell (fig. 76). In these preparations, 

 one finds an instructive variety of figures, giving an accurate idea of 

 the relation of the various parts. When most of the celi substance has 

 been removed, it is easy to see the four nuclei of the retinophorae, 

 located at the four corners of the Square, together with the two smaller 

 nuclei of the corneal cells, situated at its sides (fìg. 76). The protoplasm 

 is often torn away from the centre of the Square, leaving an irregulär, 

 round space of varying dimensions, from the middle of which projects 

 quite a large fibre, often surrounded by a group of smaller ones 

 (fig. 76). 



Below the nuclei, the cells are filled with a mass of less consistent, 

 finely granular protoplasm; then follow the conical, four cornered crys- 

 talline cones which are nearly half as long as the ommatidia them- 

 selves (fig. 73 ce). Each cene forms a Square pyramid, the four 

 quarters being produced by the thickened, axial walls of the retino- 

 phorae. Its outer end is quite finn and consistent, and is composed of 

 a refraetive, nearly homogeneous substance, which, towards the inner 

 end, becomes softer and more granular, having at the apex a tendency 

 to break up into fragments. Its diameter is only a trifle smaller than 

 that of the calyx , which it almost completely fills , and with whose 

 abaxial walls its faces are nearly parallel. Nearer the centre of the 

 eye, almost at the inner end of the crystalline cone, the opposite 

 halves of the calycal wall develop sickle-shaped, granular thickenings, 

 which increase in size as the diameter of the retinophorae dim- 

 inishes, so that the enclosed space becomes, at first, ovai and, finally, 

 round (figs. 80, 81 and 82 x). The narrowing apex of the pyramid, 



