THE AETIFICIAL INCUBATION OF OVA. 35 



a tap, to prevent tlie back-flow of the drip. I may 

 mention here another of the objections to the 

 earthenware trays. Everything is cast, even to the 

 lips or spouts. These are very liable to injury, 

 projecting as they do, and being of soft and brittle 

 material the slightest blow breaks them or knocks 

 them off completely, when the trays are almost, if 

 not quite, useless, as it is very difiicult to put a 

 supplementary spout to them, save at a trouble and 

 cost equal almost to that of a new tray ; and when 

 such a spout is put, the slightest touch deranges it, 

 and causes a leak, which not only wastes the water, 

 but makes a slop, and creates a damper atmosphere 

 than already exists, which is quite unnecessary. 

 With slate all this is needless. The spout can be 

 fitted by any village plumber without the least 

 difficulty, and at the end of the season can be taken 

 off, and put carefully away, while the trays can be 

 packed or stacked into a compact mass without 

 danger of breaking, all of which cannot be done 

 mth the ordinary earthenware trays. 



Now, we have decided that the slate tray is the 

 best for general piscicultural purposes. The top of 

 the spout, or hole through which the water runs, 

 should be three-quarters of an inch from the top 

 of the tray, so as to allow for a sudden flush of 

 d2 



