DOUBLE VISION. 113 



DOUBLE VISION. 



There is a plieuomenon wliicli has long been noticed 

 in that singular reptile the Chameleon, and long sup- 

 posed to be quite anomalous. It is that the eyes, 

 which in most vertebrate animals move only in unison 

 with each other, and as if by a common impulse, are 

 here quite independent ; the one glancing hither and 

 thither, while its fellow remains motionless, or looks 

 in different directions. 



A few years ago Mr. Lukis of Guernsey observed 

 that the same peculiarity existed in the Sea-horse 

 {H{j)j)Ocamj>us) ^ a cmious little fish of the Syngna- 

 thidce or Pipefish family. In my " Devonshire Coast" 

 I mentioned the Worm Pipefish [Syngnathus lu7yibr{- 

 ciformis) as a second example of the phenomenon in 

 this class of animals ; but I have since found that it is 

 by no means so rare as it had been supposed. All 

 the Pipefishes display it; the Suckers [Lepidog aster), 

 tiny fishes of low organization, manifest it strongly : 

 in the Little Weaver [TracMnus vijoera) I have re- 

 marked it very distinctly, and with more than common 

 admiration, on account of the unusualbeauty of the eyes 

 in this species, which resemble turquoises set in gold. 



The Wrasses [Lahridce) have the power of separate 

 motion, but in a less degree : in the Butterfly Blenny 

 {Blennius ocellaris) and the Gattoruginous Blenny 

 {B. gattorugme) it is more or less distinct, in the 

 former more than the latter. The fishes just men- 

 tioned (the Blennies and the Wrasses) have the faculty 

 of moving the two eyes in unison as well as inde- 

 joendently, apparently at pleasure. 



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