DIVIDED EYES OF CERTAIN INSECTS 46 1 



Fig. 3, B. Two of these cells are always larger than the 

 other two. Two of the plates of the pseudocones are always 

 larger when four are seen — sometimes only 2 can be found. 

 The pseudocones of the large ommatidia are wider, longer and 

 farther apart than those of the small ommatidia. Both have 

 relatively the same shape. The inner portion of each pseudo- 

 cone tapers nearly but not quite to a point. Each inner end is 

 really truncate and appears to have a funnel-like opening. 

 Extending along the line of the longitudinal axis of the pseudo- 

 cone and beginning immediately beneath the truncate cone tip 

 is the retinula. This has a darker rhabdome portion along the 

 axis from the tip of the pseudocone to the basement membrane. 

 The axis itself, however, is occupied by a very narrow light 

 band. Often, if the sections are jammed a little in the cutting, 

 the rhabdome portion takes a wavy form as shown in the frag- 

 ment at iv (Fig. 4, A). The retinulae of the large ommatidia 

 are wider, but no longer than those of the small ommatidia. 



Immediately beneath the basement membrane, in all parts of 

 the eye is a network of tracheal vessels, 2 of which are shown 

 in cross-section at tr (Figs. 3, A, and 4, A). Under the tracheal 

 network is a narrow layer of retinular-like bodies rb (Figs. 3 

 and 4, A). These bodies have their long axes parallel with 

 each other, but not always exactly parallel to the retinular axes 

 above them. Some sections show a definite fibrous or continu- 

 ous cell connection between the ends of the retinula at the base- 

 ment membrane bm, and the upper outer ends of these retinular- 

 like bodies. These connecting strands are always narrower 

 than either the retinula or the retinular-like bodies, and they 

 curve around the tracheae, often, in order to make the connec- 

 tion. It seemed impossible to demonstrate the presence of 

 retinular nuclei satisfactorily in old adult eyes used, but they 

 were easily shown at rn (Fig. 4, A), in the eye of a young insect 

 dissected from an old nymph case when the adult was just 

 ready to issue. 



Here and there along the upper part of some cells of the 

 retinular-like bodies large nuclei have been found («, Figs. 3 

 and 4, A). These nuclei appear larger than the ordinary pig- 

 ment cell nuclei. Whether they have any special significance 



