HATCHING TROUT 151 



to aid in the aeration of the water about the 

 eggs, as after eyeing they should come into con- 

 tact with plenty of free oxygen in the water 

 which flows over them. The frequency of 

 feathering will therefore depend on the amount 

 of oxygen there is in the water. Feathering 

 also assists in the prevention of the growth of 

 fungus, and in other particulars appears to be 

 an aid in successful hatching. 



Care During the Yolk-sac Period. — The num- 

 ber of fry placed in a trough is a matter of 

 discretion and ability to care for them. Almost 

 as soon as transferred from the screens the fry 

 will "huddle," as it is termed; that is, gather 

 together thickly in different parts of the trough, 

 usually in the corners and along the sides. 

 Huddling is regarded as a sign of health. If 

 the fry do not do this within a reasonable time 

 after hatching, and continue to do so until the 

 sao is partially absorbed, they are not thor- 

 oughly strong and healthy. It is possible of 

 course for the little creatures to huddle in too 

 great numbers in some particular parts of the 

 trough, so it is advisable to set low partitions 

 in the bottom, near the head and at the centre. 



