74 PHOTOGRAPHY FOR NATURALISTS. 



a weed that only grows in stagnant water is not the 

 best background for a trout. Equal care should be 

 taken with the bottom, if it is to appear in the finished 

 photograph. There is a wide distinction between mud 

 and gravel from a natural history point of view, and 

 one is as easy to insert in the tank as the other ; though 

 it must be admitted that a bottom composed of finely 

 divided material may cause considerable trouble when 

 disturbed by the movements of the subject. 



Nothing can be laid down as regards the develop- 

 ment of fish photographs other than the usual pre- 

 cautions against fog and harshness, to be observed in 

 the treatment of all very sensitive and under-exposed 

 plates. In work of this kind the writer inclines to the 

 use of metol or rodinal, followed, if necessary, by 

 careful intensification. 



It can hardly be necessary to remind readers of 

 the moral obligation to treat their prisoners with 

 humanity, but, as it is possible that a fish may be put 

 to discomfort and perhaps killed unintentionally, a 

 few words on the proper handling of fish may not be 

 out of place. That a fish should not be kept out of 

 water a moment longer than is necessary is obvious. 

 It is not so obvious that a sudden change from one 

 kind of water to another may prove fatal to a delicate 

 species. It is always advisable to fill the tank with the 

 water from which the fish is taken. Some fish are 

 much more liable to mechanical injury than others, 

 some are more nervous. The art of handling all fish 

 as delicately as possible should be cultivated. 



