INCUBATION. 91 



against which, no precautions can avail, and for 

 which no remedy can be devised. The word is 

 applied to two very different vegetable growths, 

 the one appearing upon wood when immersed for 

 the first time in the water, a gelatinoid substance 

 of disgusting appearance, but doing no possible 

 harm. We have hatched spawn surrounded on 

 all sides by this much-dreaded material, the ap- 

 pearance of which can be easily prevented by 

 coating all wood-work with black asphalt varnish, 

 or by charring. As the charring of the hatching- 

 troughs by fire has been made the subject of a 

 patent, and from ten to twenty -five dollars is 

 charged for the privilege, it may be well to men- 

 tion that strong oil of vitriol will carbonize the 

 surface of wood in a very satisfactory manner. 

 Small articles may be dipped in it, or, if the object 

 is too large, it may be rubbed with a swab ; the 

 surface should then be washed thoroughly with a 

 mixture of one ounce of salaratus to a quart of 

 water, and afterward laid for some days in a run- 

 ning stream. On this there is no patent. The 

 true byssus, however, is a different substance, 

 though also of vegetable character, and will, under 

 certain circumstances, attack and destroy spawn ; 

 but it will not at first appear unless upon an egg 

 which has been dead for at least twenty-four 

 hours. It is of a filamentous character, and the 



