EsTERLY. — Eucalanus. 



PLATE 5. 



All the figures on this plate were drawn from preparations stained in Mallory's 

 connective-tissue stain. It has been impossible to preserve satisfactorily in 

 the monochromatic reproduction the desired values of the colored drawing. 



Fig. 44. Oblique sagittal section, seen from right side. Note the membrane 

 about. the optic nerve; it is continuous with the membrane about 

 the brain (compare with Fig. 43). The eye rests upon the ventral 

 body wall; the cells of the ventral ocellus are continuous with 

 the hypodermis. The membranes which are believed to belong 

 only to the lateral ocelli are shown at the anterior end of the 

 dorsal portion of the eye. The nerves lie in the median plane 

 in the pigment cell; some fibres may be seen passing through 

 the basal plate of the median ocellus. Neurofibrillae are also 

 shown. X 830. 



Fig. 45. Anterior face of a cross section through the posterior border of the 

 eye. Twenty-eight fibres of the optic nerve are shown, two of 

 which run through the basal plate of the ventral ocellus. 



Fig. 46, Similar to Figure 44. In addition, two fibres of the optic nerve are 

 shown passing from the retinal cells into the central cell at the 

 anterior end of the dorsal portion of the eye. X 830. 



Fig. 47. Cross section of the optic nerve. Note the sheath, and a nucleus; 

 also the hypodermal nuclei. X 830. 



Fig. 48. Sagittal section seen from left side. Compare with Figures 44 and 

 46. X 830. 



Fig. 49. A cross- sect ion, immediately anterior to that of Figure 45. Thir- 

 teen optic fibres are cut in cross sections, and six leave the cells 

 of the lateral and ventral ocelli. The neurofibrillae, especially in 

 the lateral portions of the eye, may be seen to be directly continu- 

 ous with the nerve fibre. The club-shaped distal enlargements 

 of the neurofibrillae are in immediate relation to the interior 

 bodies — this being shown best in the ventral ocellus. X 830. 



Fig. 50. The next cross-section anterior to that of Figure 49. The structures 

 in the two are practically the same. But note in Figure 50 the 

 opening in the basal plate of the ventral eye through which a 

 nerve fibre passes. It is shown cut lengthwise in figures 44 and 

 48. X 830. 



Fig. 51. Sagittal section of part of the brain and an organ of Claus. The 

 membrane around the brain is shown, and the hypodermis be- 

 neath it. A nerve leaves the organ. All the structures — interior 

 bodies, nucleus, nerve — are similar to those in the median eye. 

 X 830. 



