630 William Patten 



eombined with eaeh other, until imaginary sectìons gave approximately 

 the same figures seen in actual cross sections of the pedieels. 



The pedicel is a columnar, hyaline body, capped at each end with 

 a pyramid. Just before the style is transformed iiito the pedicel, it is 

 seen to be composed of a niimber of pieces which gradually grow shorter 

 and shorter, until they are converted into a number of very thin plates 

 constituting the outer pyramid of the pedicel. The plates, however, 

 again increase in thickness. until, at the opposite end, they are again 

 converted into blocks, 10 or 12 times as thick as the outer lamellae 

 (figs. 72 and 74). The pedicel is oblong in section, and for convenience 

 we shall speak of the long and short diameters as the p rimar y and 

 seconda ry axes, and the line coincìding with the axial nerve as the 

 median , or optic axis, either of the pedicel, or ommatidium. The 

 plates are of two kinds, alternating with each other: primary oues, 

 composed of fibres , or marked with lines parallel to the primary, or 

 long axis; and secondary plates of the same composition, but with the 

 lines at right angles to those of the first, or parallel to the secondary 

 axis. 



The primary plates are lamellae which bave been reduced to thin 

 membranes along the secondary axis , while the two extremities bave 

 been transformed into ovai, or diamond-shaped figures, the short diam- 

 eters of which are equal to the originai thickness of the piate (fig. 103). 



The secondary plates are lamellae which retain their originai thick- 

 ness along the secondary axis, as well as along the faces forming the 

 broad wall of the pedicel , while the ends are hollowed to receive the 

 ovai ends of the primary plates (fig. 104:. 



In a median longitudinal section (fig. 72) , it will be seen that 

 both kinds of plates are thinnest and most numerous at the outer end 

 of the pedicel; toward the inner end, however, they increase in thick- 

 ness, especially the secondary ones. The latter. figs. 104 and 105, may 

 be regarded as compound, each one being composed of eight pieces. 

 The zigzag line divides the piate into two, while the two double 

 wedges of each half are again divided, by a horizontal plane passing 

 through the middle of each piate, into four pieces. 



I am inclined to think that, in the living condition, these plates 

 form sharp-lined and geometrical figfires, but in sections, or macerated 

 preparations, they are usually somewhat rounded. 



Each one of the primary plates is, at one end, indented by a fold of 

 the scalloped retinula (figs. 72 and 93, ì). 



Surrounding the retinophorae, are seven, oddly shaped retinulae, 



