EsTEHLY. — Eucalanus. 



PLATE 2. 



Fig. 11. Oblique frontal section of the left organ of Claus, seen from dorsal 

 side. Vom Rath's fluid 18 hours; decolorized in hydrogen per- 

 oxide. The two cells composing the organ are shown, and their 

 basal plates; the interior bodies lie near the periphery of the cells. 

 The striate appearance of the cell contents should be noted. X 

 665. 



Fig. 12. Dorsal aspect of a frontal section of the same organ of Claus as is 

 shown in Figure 11, but the succeeding section and before de- 

 colorization. It shows the blackening effect of vom Rath's fluid 

 on the basal plates, and that the basal plates of two cells look 

 like a single body suspended in a vesicle. X 665. 



Fig. 13. An organ of Claus seen from the ventral side. Vom Rath's fluid 

 18 hours; pyroligneous acid 4i hours, decolorized in hydrogen per- 

 oxide. The ventral cell with strong outline has been drawn in 

 detail; the dorsal cell is outlined very faintly. X 665. 



Fig. 14. A drawing of the organ of Claus from which Figures 13 and 15 were 

 also drawn. In Figure 14 the focus was fixed at about the middle 

 of the thickness of the organ, to show how the combination of the 

 basal plates of the two cells gives rise to the appearance of a solid 

 body suspended in a vesicle. X 665. 



Fig. 15. The dorsal cell of the organ of Claus, the remaining portions of which 

 are shown in Figures 13 and 14. 



Fig. 16. Anterior aspect of a cross section of eye. Zenker; iron-haema- 

 toxylin; orange G. The difference in appearance between the 

 nuclei of retinal cells and of hypodermal cells is shown, as well as 

 the relation of the tapetum and basal plates. X 665.' 



Fig. 17. Very oblique cross section (partly frontal) of eye. Vom Rath's 

 fluid 24 hours. Particularly favorable for showing a typical ar- 

 rangement of the interior bodies, and the striation of the inner 

 ends of the cells. The arrangement of the interior bodies corre- 

 sponds with the direction of the fibres in the optic nerve outside 

 the eye. X 665. 



Fig. 18. A cross section through the anterior part of the brain seen from in 

 front. (Compare Plate 6, Figure 61.) Vom Rath's fluid 24 hours; 

 decolorized with hydrogen peroxide. The left organ of Claus is in 

 contact with the nerve of the first antenna; the brain, nerve, and 

 organ of Claus rest upon the hyodermis. The striate appearance, 

 due to the arrangement of granules in the cells of the organ of Claus, 

 is shown. X 665. 



Figs. 19, 20. Frontal sections of an organ of Claus, seen from the dorsal 

 side. Vom Rath's fluid 18 hours; decolorized in hydrogen per- 



