WHAT THE FISHES SEE 



have branched tentacles like plumes which serve as 

 tactile organs. But the basilisk blenny has none. Its 

 small head, absolutely bare, with a thick crest on the top 

 like that on a helmet, with a snout curved like a beak, 

 reminds one of the head of a parakeet. Its greenish- 

 grey body, with a suspicion of rose, barred and striped, 

 seldom exceeds six to eight inches in length. But 

 despite its small size, it does not pass unnoticed whether 

 it is resting on its pelvic fins or swimming in its un- 

 dulating fashion. 



It is particularly common in the warm southern 

 regions of the Mediterranean. The aquarium of the 

 oceanographic observatory at Salambo in Tunisia has 

 always several specimens in its tanks. I have had the 

 opportunity of studying them there and noting the 

 perfection of visual sensation, a perfection which I have 

 never observed with such clearness or so consistently in 

 any other species of fish. 



The two eyes are small, but brilliant and protruding. 

 Not far from one another, on each side of the projecting 

 crest of the snout, they are set in a kind of hook-nosed 

 face. They do not simply reflect the luminosity from 

 without, they shoot glances here and there; these small 

 creatures actually look about them as a land animal does. 

 Their movements are suitably co-ordinated, and they 

 turn together in the direction in which they have to look, 

 and so secure the advantages of binocular vision. To 

 make this exception still more marked and clear, the 

 head, as a result of a flexible articulation not possessed 

 by other fishes, can turn a little to the side at which the 

 eyes are looking, thus co-ordinating their sensations 

 and improving their vision. This is a really remarkable 

 arrangement which allows this fish to direct its sight 

 as a land vertebrate does, and turn its head to see the 

 better. It is a surprising example of adaptive re- 

 semblance in a species which has no sensitive plumes, 

 but seems to make up for the lack of them by an improve- 

 ment in its powers of vision, and by movement of the 



*S3 



