68 DOMESTICATED TROUT. 



space, makes the handling of the eggs simpler and 

 easier, and provides an easy way of getting rid of 

 sediment. These points will appear as each particu- 

 lar method now in use is taken up in turn. 



Various Methods of Using Hatching Trays. 



There may be other ways of employing wire trays 

 for hatching purposes, but those which have come 

 particularly under my observation are six in number, 

 and may be enumerated as follows : — 



(i) The one-tier method ; (2) the double-tier meth- 

 od ; (3) the Williamson method ; (4) Clark's method ; 

 (5) Holton's method ; (6) the use of deep trays with 

 the Williamson hatching troughs. 



1. The one-tier method consists simply in covering 

 the bottom of the common hatching troughs with 

 shallow trays raised about half an inch from the bot- 

 tom, to allow the water to flow under as well as above 

 the eggs, and also to give the sediment that collects a 

 place to settle in, out of the way of the eggs. The 

 water is turned through the trough as usual, and there 

 is nothing else peculiar about the use of the trays be- 

 sides what has just been mentioned. If there is much 

 sediment in the water, this method is a vast improve- 

 ment over the old one of placing the eggs on the bot- 

 tom of the troughs ; for while there is a space under- 

 neath the trays for the sediment to settle in, it can 

 always be kept off the eggs. This plan is usually 

 adopted in trout-hatching establishments where the 

 sediment is very troublesome. It is not patented. 



2. The double-tier system consists in placing one 



