How to obtain it. 205 



much of the nature of their food as to become highly poisonous 

 to the fish, when it, or the water in which they live, is of an 

 unwholesome character. There is here a very wide field for 

 research, for which we want some workers. 



As already stated, the plan to adopt for the cultivation of 

 these creatures is, first of all, to protect them from their enemies. 

 As trout are their enemies by nature, therefore they must be 

 protected from them ; and this brings us to the point of having 

 separate or accessory ponds in which to cultivate a sufficient 

 amount of food. At Gremaz, in France, the food is cultivated, 

 and the fish are herded from pond to pond, very much as sheep 

 are penned off on turnips, and are moved from one pen to another 

 as the crop is devoured. What I conceive to be a better way, 

 and one that I have adopted for many years, is to grow the food 

 in separate ponds, to which the fish have no access. 



Either plan may be equally good, and probably is so. It 

 just resolves itself into a case of which is most workable. In our 

 cold northern climate we must adapt ourselves to circumstances. 

 With these ends in view, an excellent plan, then, is to provide 

 special ponds, well stocked with plants, for the production of the 

 natural food of the trout. In this way a natural supply may be 

 obtained, and maintained, but if once the trout gain access to the 

 food pond, the result will probably be the entire depletion of the 

 stock of fish food. 



One of the best animals to cultivate is the water flea \ 

 (Daphnia.) Though so called, yet it is not in reality a flea, although 1 

 in general appearance it bears some re- 

 semblance to Pulex trritans, its " longshore " 

 namesake. There are some ten varieties, 

 varying in size from three sixteenths to one 

 sixteenth of an inch in diameter. The 

 commonest species is Daphnia pulex, which 

 varies in colour and size considerably, accord- 

 ing to the nature of its surroundings, and also 

 Fi 23. to the time of year. It is semi-transparent, 



Daphnia pulex, enlarged. * 



and usually of a reddish tinge, and swims 

 with a jerky movement ; its food consists of small infusoria and 

 vegetable matter. It thrives best in moderately still water, and 



