io8 NATURE AND THE CAMERA 



the moment when about to make the exposure, dis- 

 turb the water's surface with your unemployed hand. 

 It is surprising what a good effect is produced by this 

 trick. 



A peculiarity that is most noticeable among the 

 highly coloured tropical fish is the power that they 

 have of changing their colour and their markings. 

 Take, for example, some of the porgies, that large 

 family of fish so abundant around Key West. The 

 same fish might be photographed ten times in as 

 many minutes, and no two photographs look like 

 the same species. The fish is beautifully marked 

 with vertical bars, pink, blue, yellow, green, and 

 brown being the prevailing colours; and yet one pho- 

 tograph will show a plain silver-coloured fish, abso- 

 lutely lacking in marks of any kind, another will 

 show faint irregular blotches, another slight indica- 

 tions of bars, and yet another will show the fish in 

 all the glory of its full markings. The yellow-fin 

 grouper, still more pronounced in the pattern of 

 its markings, though scarcely so brilliant in colour, 

 will change in an instant from a pale, sickly yellow 

 with the markings only just discernible to a rich 

 green with markings of very dark brown and bright 

 red. Whether these changes are voluntary or not is 

 scarcely known, and anyhow this is not the place to 

 discuss that interesting question ; but the surroundings 

 will usually be found to have some effect on the colour 



