CHAPTER 6 



THE EYES OF ROUND WORMS, 

 NEMATHELMINTHES 



Many of these, such as Ascaris lumbricoides, A . suilla, A . megalocephala, 

 Dochmius duodenalis, Oxyuris, Trichina spiralis, Filaria medianensis 



Op.n. 

 Ol.n.- 



Fig. 55. 



A — Dorsal aspect of head of Sagitta bipunctata, showing paired eyes connected 

 by optic nerves with the brain. 

 E. : eye. Ol. n. : olfactory nerve. 



Op. n. : optic nerve. Br. : brain. 



Ol. 0. : olfactory organ. 



B — Section through eye of Sagitta hexaptera, after O. Hertwig. 

 Ep. : cutaneous epithelium. Rh. : rods. 



L. : lens. Ret. c. : retinal cells. 



P. : pigment. 



(guinea worm), F. sanguinis hominis, and Trichocephalus dispar, are parasitic 

 and have no eyes. Among the non-parasitic round worms, which live in 

 fresh-water near the sea-shore or on the surface of the ocean, we may 



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