42 FISH CULTTTEE. 



fervse, and advised a filter to be applied. There was 

 some difficulty in applying it ia a mechanical point 

 of view, and it proved fortunate, indeed, as matters 

 turned out, that the temperature of the water did not 

 permit the confervse to grow. Had it done so, I fear 

 that hardly an egg would have escaped — for being 

 desirous of watching the entire process closely, my 

 friend deposited the ova on the gravel instead of 

 under it, and thus all sediment settled directly on 

 the ova. 



A rough filter, in such cases, is very desirable; 

 one of the large-size flower pots, with side holes, 

 every hole being corked but one, would, I imagine, 

 answer well enough, a layer of fine gravel being 

 placed in it first, say two inches deep ; then a layer 

 of charcoal, of the size of beans and peas, and then 

 another layer of gravel; turn the water on to this, 

 and, I think, a filter effective enough would be the 

 restdt ; a spare one should be kept at hand, to ex- 

 change in case of the fiJ.ter getting fouL'' Half of the 

 troughs were filled to within an inch of the small 

 delivery pipes, noted above, with fine gi-avel well 

 boiled. The other half had, over beds of gravel not 

 quite so high in the boxes, planes of slates fitxed; 



' "With streams a bed or bank of sand and gravel will form a very 

 tolerable filter. 



