344 TOILERS IN THE SEA. 



different sexes. At a certain time the eggs are 

 emitted by the female, and rest within the folds of 

 the respiratory organs, awaiting fertilisation by the 

 male element. This latter is diffused promiscuously 

 in the water, " the organic particles, disseminated 

 through the surrounding water, are carried away by 

 the currents, and some of them thus make their way 

 into the respiratory organs (branchiae) of the females, 

 where they meet with the eggs, and vivify them by 

 contact. If we could only destroy the vitality of 

 these organic particles, before they come in contact 

 with the eggs, we could at once put a stop to the 

 further development of these destructive mollusks. 

 If a twenty-millionth part of a mercurial salt be 

 thrown into the water, in which myriads of these 

 organic corpuscles were moving, it would be sufficient 

 to render all of them motionless, in the course of two 

 hours. A two-millionth part of the same salt pro- 

 duces the same effect in forty minutes, and entirely 

 deprives the water of the fertilising power, with which 

 it had previously been so highly charged. To pre- 

 serve the submerged wood of our marine docks, and 

 wharfs, it is therefore only necessary, from time to 

 time, to throw a few handfuls of these different sub- 

 stances into the surrounding water. Fecundation 

 would thus be entirely arrested, and the eggs would 

 perish before they were developed, and consequently 

 the species would be completely exterminated, in our 



