PEOPAGATION OF FISH. 239 



spermatozoa, little tadpoles as they appear to be under 

 the microscope, were not fond of water, and although 

 very active when first emitted, soon perished in it. They 

 retained their vitality rnuch longer when dropped. among 

 the ova in a comparatively dry state, and this is the method 

 universally pursued at present. The result of the change 

 was very great ; on the earlier plan not more than one egg 

 in three or four was vitalized, whereas now, fully ninety- 

 eight per cent, are made capable of producing young. 



In selecting a place for trout hatching, it is essential to 

 have one where the water is at an even low temperature, 

 near to the springs if possible, and where there is abso- 

 lute security from muddy drainage or overflow from 

 rains. The shape of ponds is not important, if the water 

 is abundant and cold enough. 



It is best, if possible, to have ponds so arranged that 

 they can be entirely drained. This is necessary, some- 

 times, for cleaning or repairing them, and changing the • 

 fish from one pond to another. If the slope of the 

 ground is sufficient to permit of such an arrangement, it 

 will often save much labor in pumping or bailing. The 

 drain pipe may be of pump logs, tile or pipe of any 

 kind, and should be fixed in the lowest part of the bot- 

 tom, or as near it as the level of the ground will allow. 

 Still better would be a regular fiume reaching from the 

 bottom of the pond to the top. A bulkhead may be put 

 in to raise the water as high as may be required, and a 

 wire screen the whole size of the flume set a short dis- 

 tance in front of the bulkhead. This large screen has 

 an additional advantage, as the larger the screen the less 

 liable it is to clog up with leaves and moss, and the 

 greater will be the volume of water passing through it. 



