EsTERLY. — Eucalanus. 



PLATE 1. 



Fig. 1. The median eye seen from the dorsal side. Entire preparation, fixed 

 in vom Rath's fluid 12 hours. The optic nerve is shown, also the 

 frontal nerves. There is some indication of the typical arrange- 

 ment of the "interior bodies" or "phaosomes," in the retinal cells. 

 The nine nuclei in each of the lateral ocelli are shown. X 270. 



Fig. 2. Frontal section through the lateral ocelli, seen from the dorsal side-. 

 Zenker; iron-haematoxylin ; orange G. Optic nerve fibres are 

 seen converging to form the optic nerve. The nucleus of the cen- 

 tral or pigment cell and the tapetum, which covers its outer faces, 

 are both shown. X 665. (Cf. Plate 6, Fig. 59.) 



Fig. 3. A parasagittal section of the eye, seen from the left side. Mallory's 

 connective-tissue stain. The tapetum lies on the margins of the 

 central cell, dorsal to the ventral ocellus, and ventral to the lateral 

 ocellus. The basal plates are shown in part on each of the ocelli 

 and it can be seen that the ventral ocellus is merely a thickening 

 in the hyjjodermis. Five of the optic nerve fibres (fbr.) cut across 

 are shown in the central cell. X 665. 



Fig. 4. Sagittal section of the brain, to show optic nerve entering at its 

 anterior end, and the optic neuropil. Mallory's connective-tissue 

 stain. X 270. Compare with Figures 35 (Plate 3), 42 and 43 

 (Plate 4). 



Fig. 5. Frontal section similar to that shown in figure 2. Vom Rath's 

 fluid 24 hours. The basal plates and tapetum have stained in- 

 tensely black. The arrangement of the interior bodies (pha'so.} 

 in the cells is typical. X 665. 



Fig. 6. Sagittal section of entire eye seen from the right side. Zenker ,- 

 iron-haematoxylin. The ventral ocellus lies in the hypoderrais,. 

 and the basal plates are shown on its dorsal surface. The optie 

 nerve is made up from three sets of fibres, which lie in the plane 

 of the section; the fibres from the ventral ocellus pass through, 

 and posterior to, the basal plate. X 665. Compare with Figure 

 51 (Plate 5). 



Fig. 7. Transverse section through the middle of the eye. Vom Rath's; 

 fluid 18 hours. Intended to show principally the cells of the eye 

 and the arrangement of the interior bodies with reference to the 

 long axes of the cells. The finely striated character of the basal 

 parts of the retinal cells is shown. X 665. (Cf. Plate 6, Fig. 58.) 



Fig. 8. Frontal section of ventral ocellus. Zenker; iron-haematoxylin; 

 orange G. The ten retinal cells and their nuclei are shown. The 

 arrangement of the interior bodies in the cells is typical. Rod- or 

 spindle-shaped bodies are shown, as well as the ribbon-like forms. 

 X 665. 



