FISHES 



Figs. 287 to 291. — The Eyes of Typical Fishes. 



275 



Fig. 287. — The sturgeon, Acipenser 

 sturio {Chondrostean). 



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Fig. 289. — The cod. Gndus morrhna (Teleostean). 



Fig. 290. — The ray. Raja clavata 

 (Selachian). 



Fig. 291.— The dogfish, Squaluf 

 aranthias (Selachian). 



(Reproductions of five of the beautiful engravings of D. W. Soenimerring, 

 1818. The reproductions are life-size and each represents the lower half of a 

 horizontal section of the left eye.) 



Vision under water requires an eye relatively hypermetropic to 

 vision in air ; moreover, the resistance of water while swimming is 

 considerable and, therefore, as an optical and a streamlining device 

 particularly among actively swimming fishes, the tendency is towards 

 a flattening of the anterior segment of the globe. The typical section 



