Fish- Hatching in a Current of Water. 99 



gravel in shallow boxes, and allow a brisk 

 current to flow over them. The dead ova 

 must be removed, or they soon generate a 

 byssus or fungoid growth, which is fatal to any 

 live ovum which it touches. This fungus grows 

 with such rapidity that in a few hours it extends 

 its thread-like arms and catches any living egg 

 within reach, inevitably causing speedy destruc- 

 tion of the vital principle. Another danger in 

 hatching is the slimy deposit, which falls even 

 from the purest water, if not well filtered. 

 The remedy for this is a good filtering arrange- 

 ment, and the use of a garden watering-pot to 

 wash the ova with a brisk shower, when any 

 deposit becomes visible. The slime is injurious 

 in preventing the proper supply of oxygen, 

 required by the egg to vivify the embryo, from 

 reaching it, and if the deposit be allowed to 

 remain long on the ovum, it causes certain 

 death to the embryo. The temperature of the 

 water is another very important point, and the 

 coolest water is to be preferred, as fish hatched 

 in cold water are said to be more robust than 

 those hatched at higher temperatures. A good 

 spring, if not impregnated with any injurioiis 

 mineral substance, is the best, as the tempera- 



