AMPHIBIOUS VISION IN TELEOSTS 



431 



Amphibious Vision in Teleosts — It is only among the teleosts that 

 we find fishes which spend enough time out of water to have any possible 

 use for air-and-water vision. The number of such teleosts is surprisingly 

 large. To mention the best known cases, there are the true flyingfishes 

 (but not the 'flying' gurnards) , the imitative hatchet-fishes {Gasteropele- 

 cus, Thoracochdrax, et al), and the butterfly-fish or 'freshwater flying- 

 fish', Pantodon. These forms come out of water for an appreciable frac- 

 tion of a minute at a time — ^up to 40 seconds, in flyingfishes — though 

 they are not amphibious inasmuch as they never come on land, or on 



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Fig. 145 — Periophthalmus koelreuteri. 



a, entire animal, x 'A. After Hess, b, eye in vertical sertion. From Franz, after Karsten. 

 c- primitive cornea; /- anchorage of suspensory ligament of lens; /- secondary speaacle. 

 c, d, e, positions assumed by the eyes of Periophthalmus, Boleophthatmus, et al, showing 

 alteration of visual lines and formation of transitory lower lids. Redrawn from Hein. 



board ship, except as a fatal accident. Nothing much is known about the 

 eyes of any of them. Then, there are such fishes as the 'climbing perch', 

 Anabas, which emerge onto land for periods limited by the considerable 

 oxygen content of their labyrinthine water reservoirs; and some blennies 

 which perch on rocks for long periods with the tail kept in the water for 

 respiratory purposes. Again, the eyes of these fishes are largely unstudied, 

 though Anabas is known to be emmetropic in water and to have no 

 accommodation — hence, a forbidding degree of myopia in air, with the 

 eye probably almost useless in that medium except for brightness- and 

 shadow-perception. 



