20 bulletin: museum of comparative zoology. 



reference to the long axes of the cells is shown to exist. Figure 5 

 (Plate 1) gives a fair general idea of a frontal section taken at a plane 

 about midway between the nuclei of the median cells of the dorsal 

 and middle groups. Even with the irregular and ragged appearance 

 of the interior bodies (pha'so.) in the cells at the anterior edge of the eye, 

 it is plain enough that they have a definite orientation in relation to 

 the lone; cell-axes. Likewise, in the central cell there is a similar 

 arrangement of the rod-like structures, which lie in a direction parallel 

 to the line joining the anterior and posterior angles of the cell outline. 

 Inspection of Figure 2 will show that in this case, also, the conditions 

 are similar. 



In the ventral eye, frontal sections give the best idea of the arrange- 

 ment of the interior bodies in the retinal cells. Figure 8 (Plate 1) 

 shows, in its general features, the condition that appears in all cases. 

 The interior bodies are arranged with reference to the long axes of the 

 cells, except in the case of the anterior paired cells. This arrange- 

 ment is least apparent in the central retinal cell, but this is the cell in 

 which the "sides" are more nearly equal than in any other. Sagittal 

 (Plate 1, Fig. 6) and cross sections (Plate 1, Fig. 7; Plate 2, Fig. 23) 

 show that there is a somewhat similar disposition of the interior bodies 

 as regards the dorso- ventral axes of the cells. 



In preparations of the entire eye, the interior bodies may be seen 

 to have the same arrangement that is shown in sections. Figure 1 

 shows this in a rather vague way for the lateral eyes. But in Figure 



21 (Plate 2), where the representation of the interior bodies is believed 

 to be accurate, as far as they are shown, their arrangement in the 

 ventral eye is much like that shown in Figure 8 (Plate 1), particularly 

 as regards the anterior cell. In the other cells of the eye, especially 

 the paired ones, the arrangement corresponds in a general way to that 

 in Fio-nre 8. All the interior bodies that could be seen in the retinal 

 cells of the vcniral ei/e have been shown in black. 



The definite arrangement of the interior bodies with reference to 

 the long axis of the cells appears in general, and in every cell, in any 

 preparation But if the attempt is made to discover whether every 

 interior bod - is so arranged, it will be seen that there are many ex- 

 ceptions; and ne such appear in all of the figures. It is possible 

 that such e: - ,.tions may be more apparent than real, owing to the 

 plane *u whic.i a section is cut, but they are none the less difficult of 

 explanation. There can be no doubt, however, as to the general facts. 



The correspondence in arrangement that appears in cross and 

 sagittal sections of the eyes, leads one to question whether the interior 



