. The Cambridge natural history. Zoology. 396 FISHES CHAP. XIV depressions, but, as a rule, when one of them is present the other is absent. It is probable that both these structures were associated with sensory organs, of which one may have. Fig. 228.—Vertical section through the parietal eye and the pineal vesicle of Petro- myzon mariniKS. c.t. Connective tissue ; p, pellucida ; p.o, pineal organ ; pt,Oj parietal eye ; /•, retina ; iii i>, third ventricle. (From Wiedersheim, after Stud- nicka.) been a parietal eye and the other a pineal eye. Some Teleosts (e.g. many deep-sea Scopelidae) h

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. The Cambridge natural history. Zoology. 396 FISHES CHAP. XIV depressions, but, as a rule, when one of them is present the other is absent. It is probable that both these structures were associated with sensory organs, of which one may have. Fig. 228.—Vertical section through the parietal eye and the pineal vesicle of Petro- myzon mariniKS. c.t. Connective tissue ; p, pellucida ; p.o, pineal organ ; pt, Oj parietal eye ; /•, retina ; iii i>, third ventricle. (From Wiedersheim, after Stud- nicka.) been a parietal eye and the other a pineal eye. Some Teleosts (e.g. many deep-sea Scopelidae) have a transparent, convex, cornea-like prominence on the upper surface of the head which may be related to one of these singular organs.^ ^ Chun, loc. cit. p. 536, . Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Harmer, S. F. (Sidney Frederic), Sir, 1862- ed; Shipley, A. E. (Arthur Everett), Sir, 1861-1927. ed. [London, Macmillan and Co. , Limited; New York, The Macmillan Company