120 DOUBLE VISION. 



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 

 (Hippocampus) a curious little fish of the Syngna- 

 ^A««?« or Pipefish family. In my "Devonshire Coast" 

 I mentioned the Worm Pipefish {Syngnathus lumbri- 

 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 {Lepidogaster), 

 tiny fishes of low organization, manifest it strongly : 

 in the Little Weaver {Trachinus vipera) I have re- 

 marked it very distinctly, and with more than common 

 admiration, on account of the unusual beauty of the 

 eyes in this species, which resemble turquoises set 

 in gold. 



The Wrasses {Lahrid(s) have the power of separate 

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

 {Blennius ocellaris) and the Gattoruginous Blenny 

 {B. gattorugine) 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- 

 pendently, apparently at pleasure. 



These are all the species in which I have noticed 

 the phenomenon of separate eye-movement, but I 



