REARING 177 



deep spring there should be very little trouble from 

 sediment ; but if your supply for the hatching-boxes 

 is taken from a river or burn, constant attention will 

 undoubtedly have to be given to the filtering arrange- 

 ments, otherwise damage will ensue. 



A suitable kind of filter consists of a wooden box 

 containing three or four screens made by tightly 

 stretching flannel on wooden frames. These screens 

 fit in grooves cut to receive them in the sides of 

 the filter-box at intervals. The interior of the box 

 is charred in every part. An extra set of screens 

 accompanies each box ; so that when one set has 

 become choked, another may be substituted while 

 the screens first used are being dried and cleaned. 



The process of hatching trout-eggs with proper 

 modern apparatus does not involve heavy labour, 

 Nor does it present difficulty or demand special skill. 

 Indeed it has been described by Livingston Stone as 

 * the very simplest and surest of all the branches of 

 trout breeding.' At the same time patience is required. 

 The stages of development of the embryo in the egg 

 occupy a considerable time. The length of time is 

 mainly dependent on the temperature of the water. 

 With an average temperature of 48 degrees Fahrenheit 

 the eggs will hatch in about fifty -three days from the 

 time when first laid down. 



N 



