CH. VI MARINE FAUNA OF TALIS SE SHORES 113 



coloured reef fishes that I caught, and I am never Hkely to 

 forget the excitement and pleasure I experienced noting 

 its brilliant colours. Its body was of a dark green colour 

 verging into pink below from the middle to the tail, 

 and bore in this region four pale blue stripes running 

 nearly parallel with one another across the back. Its head 

 and shoulders were of a brighter colour, and bore three 

 stripes of bluish-green, the middle one of which spectacled 

 across the bright orange-pink eyes. On each side of the 

 tail there were three rows of bright transparent spines, 

 each of them standing on a pit of dark brown pigment, so 

 that they had the appearance when casually examined of 

 small eye-spots. In the tail region the nerve of the lateral 

 line on either side divides into three branches, one of which 

 Hes immediately beneath each of these rows of spines : and I 

 have traced a small nerve from these branches running to 

 each of the pits or rings of pigment on which the spiny 

 scales stand. Whether in the youngest stages, when the 

 spines are quite transparent, these organs can be affected 

 by the rays of light, and thus function as rudimentary 

 optic organs, cannot at present be determined, but I am 

 inclined to believe that they do. Whatever their exact 

 function may be, however, there can be no doubt from 

 their nerve-supply that they are very highly sensitive 

 organs. 



In the older and larger trigger-fishes the spines become 

 long, hard, pointed, and bent over towards the head. They 

 are then undoubtedly used as organs of defence. It is a 

 curious thing that, besides the Balistidse, nearly aU the fishes 

 of the genera Naseus and Acanthurus, also reef- feeding fishes, 

 are similarly provided with defensive spines upon their taUs. 

 There is some mystery about them, though, which requires 

 to be cleared up. If, as may be supposed, their enemies 

 catch them by the tail when they are browsing among the 



