THE ARTIFICIAL INCUBATION OF OVA. 4i 



a large flower-pot, some fifteen inches deep, stopping 

 all the side holes (which such large pots usually 

 have) but one, and fixing on that a short leaden 

 pipe. The entrance to the pipe requires to be fenced 

 by means of a piece of perforated zinc, or the fine 

 gravel and sand will work through it. About once 

 a fortnight the contents must be taken out and 

 carefuUy washed and cleansed and then restored. 

 To do this properly it is advisable to have two 

 pots, so that one shaU be always ready to put up 

 when the foul one is removed. This will be found 

 a capital safeguard against vermin or filth, and very 

 little but fairly pure water will pass through it ; 

 but it offers no material hindrance to that, and 

 any reasonable stream will run through it with suffi- 

 cient quickness for almost any requirements. As an 

 additional safeguard, however, I always let the water 

 faU into a perfectly empty tray before it is conveyed 

 to the trays with ova in them; for one cannot 

 always be sure that some kind of dirt or objection- 

 able matter wiH not find its way tlirough, but by 

 the above means the chances of damage are greatly 

 reduced. 



Now we come to the question of how many 

 trays it may be desirable to use ; for according to the 

 number so you must increase the stream of water. 



