THE BAY OF BISCAY. 229 



arc about to experience their last metamorphosis, the 

 young Teredos leave the branchiae of their mother, 

 and, fixing themselves upon the first piece of wood 

 that presents itself, begin to construct their galleries, 

 and from this moment they are entirely protected 

 from all external attacks. It is therefore necessary 

 to destroy them before this period, or, what is at 

 once more certain and more economical, we must 

 prevent their birth. To attain this object it is suffi- 

 cient to dissolve in the water which the mothers re- 

 spire, an infinitely small quantity of a salt of mercury, 

 lead, or copper. 



Physiology teaches us that the egg, or female 

 element, produced by the mother requires to be 

 brought in contact with a special element secreted 

 by the male, in order that it may be fertilised and 

 become developed into a living being. In all ani- 

 mals that have hitherto been examined, this secretion 

 when observed under the microscope has been found 

 to contain minute organic particles which move with 

 extreme rapidity. When submitted to the action of 

 various reagents, these corpuscles comport themselves 

 in the same manner as the Infusoria ; various poi- 

 sonous agents and electric shocks at once putting a 



as examples. The eggs, or rather the young which proceed 

 from them, pass the whole of the winter in the branchial folds of 

 the mother. I was enabled for several months to follow the develop- 

 ment of these Molluscs, of which I kept several by me in a tub of 

 water. The memoir which I published in reference to this subject 

 in 1839, was the first which I addressed to the Academy of Sciences 

 at a period when I certainly had no hope that I should ever attain a 

 place among that distinguished body. 



Q 3 



