THE PHOTOGRAPHY OF FISH. 65 



fish as a living one, as swimming, for instance, with a 

 printed-in background. With a discerning critic such 

 an attempt will stand self-convicted, while it may easily 

 mislead the general public. 



When we commence to tackle the living subject the 

 following difficulties immediately present themselves : 

 I, The mobility of the fish, which necessitates very 

 short exposures ; 2, the great loss of actinic power in 

 white light, resulting from its passage through glass 

 and water ; and 3, in some cases, the delicacy and terror 

 of the subject under operation. To counteract the 

 first of these difficulties the writer has adopted the 

 principle of the animalcule tank employed in con- 

 nection with the optical lantern ; in other words, he has 

 confined the fish in such a way that its swimming 

 movements are restricted to the space enclosed between 

 two parallel planes, while it suffers little or no dis- 

 comfort. It may not be amiss to give his experience 

 with the various forms of tank employed. 



As a preliminary experiment, two equal-sized pieces 

 of window glass, with a U-shaped piece of indiarubber 

 gas-tubing between them, were tightly bound together 

 with wire at the extremities. The result was a tank 

 whose ends and bottom were formed by the indiarubber 

 tubing, and whose sides were formed by the glass. 

 The width between the glass sides was about half an 

 inch. The tank was supported out of doors in bright 

 sunshine and filled with ditchwater. Some twenty or 

 thirty sticklebacks were then inserted. The focussing 

 presented no particular difficulties, a size of picture 



