How to obtain it. 203 



as well as friends to encounter, and by cultivating haphazard all 

 the aquatic creatures that we come across, we may be doing harm 

 instead of good. There are probably few of the minute organisms 

 which we meet with which are not devoured with avidity by large 

 trout, but there are many which, if introduced into a fry pond, 

 would soon reduce the stock of fish contained therein considerably. 

 This is one cause by which trout sometimes seem to die 

 < unaccountably in the fry stage. I have seen, years ago, thousands 

 of little fish dropping down dead from no apparent 

 reason. It has since been ascertained that these had 

 probably been attacked by parasites. 



There are myriads of small creatures, which are 

 highly useful as food for fry, known as infusoria. 

 Some of the best known among these are probably 

 the Rotijera (commonly known as rotifers or wheel- 

 insects), but they are very minute, and as far as our 

 Fig. 22 present knowledge has attained cannot be cultivated 



Rotifer, enl g. . 



on a commercial scale. 



The secret of the successful cultivation of most, and probably 

 all the minute forms of life, lies largely in the protection of them 

 from their natural enemies. The same lines have to be followed 

 as in the case of large game. We must provide for them safe 

 undisturbed breeding grounds, and suitable food. We often find 

 that Nature works out these deeply interesting matters with 

 unerring exactitude, making due provision for everything. Nothing 

 is overlooked. Now, it does not suit Nature's purpose to have 

 great crowds of any individual creature in one place, except in a 

 few exceptional cases, and hence there are many causes which 

 tend to keep in check the superabundance of life, which would 

 otherwise be found existing. The same applies to the fish. We 

 do not find a pool in the natural stream, as a rule, abounding in 

 fine large trout. We know that this is the exception ; but we 

 also know that it can be brought about by artificial means. 



So, then, with the more minute forms of life. If we apply 

 the same rules that attach to the cultivation of the fish, we obtain 

 the same result, viz., an enormous multiplication of individuals. 

 Whilst multiplying the fish on the one hand, we must multiply the 

 creatures on which the fish feed on the other, and so the two 



