32 J BULLETIN OF THE UNITED STATES FISH COMMISSION. 



dently superfluous after what had taken place in the closed aud poorly 

 aerated waters of the claire where we had in the first place established 

 ourselves. We knew, in fact, that the person who cultivated the marsh 

 had attempted in vain, two or three years before, to collect spat. But, 

 in undertaking this counter-experiment, we had a two-fold object in 

 view, viz, to clear up all doubts, if such still existed, as to the value 

 and advantages of the method of artificial fecundation, and that of 

 creating a sentiment in its favor. This proof had to be conclusive. 



At the entrance to a fish-pond close to the one used by us, of nearly 

 the same extent, similarly arranged and receiving water from the same 

 canal, had been placed the tiles upon which it was thought the spat 

 coming from the river would not fail to attach itself. At that time the 

 oysters were in the height of reproductive activity; the collectors in 

 the Giroude were being charged with spat, and ours in the other pond 

 were being covered as fast as and in the proportion that they were im- 

 mersed. We expected to find some young oysters on the collectors put 

 down as a test. There was nothing on them, however; these collectors 

 remained completely free of all traces of spat. 



THE METHODS OF ARTIFICIAL FERTILIZATION. 



Imperfect and incomplete as our methods of artificial fertilization 

 still are, we think it useful to make them known. In fact, there is no 

 better way perhaps to aid in bringing them to that perfection of which 

 they seem to be susceptible. After many trials and experiments, we 

 have found the following to be the most practicable: 



It is easy, after a little practice, to determine the sex of the Portuguese 

 oyster with the naked eye. A small portion of the matter contained 

 in the genital gland is taken and placed on a plate of glass and diluted 

 with a quantity of sea-water many times in excess of the volume of 

 the portion of spawn. 



When the subject is female, the liquid appears granular, and upon 

 examining it with care we see the ovules which the water lias set free 

 or separated. If it is a male, the mixing of the water with the seminal 

 fluid is more difficult, and the liquid remains opaque and milky. With 

 the aid of a pocket lens the distinction is very easily made. 



The choice of spawning individuals is not, we have reason to think, 

 a matter of indifference to the success of the operation. We would 

 reject for this purpose oysters from shallow water or such as are fre- 

 quently uncovered by the tide.* We have never obtained good results 



" Our belief as to the sterility of certain brood-oysters rests upon two very impor- 

 tant observations made al the island of Oleron. It was in vain that we attempted to 

 fertilize the spawn of oysters taken from the higher levels of the oyster grounds of 

 tli<- island, while at the same time, under the same conditions, in the same medium, 

 with the same water, and under the same external influences, the experiments resulted 

 in the formation of mobile embryos, if spawners were used from the same shore, but 

 from deeper water. We would, however, make certain reservations in this regard. 



