HIILLETIN OF THE UNITED STATES FISH COMMISSION. 229 



water; wo put in the liquid at iutervals of from five to ten minutes. 

 During tbat time tlie eggs readied tbe bottom of tlie vessel, carrying 

 with them the spermatozoa which surrounded them. There remained 

 floating only infecuud eggs, the overplus of spermatozoa, and organic 

 matter. Then, by means of a siphon and auother reservoir we caused a 

 current of water to pass into the glass vessel, regulating the flow in 

 such a manner as to let in during one hour a quantity of water almost 

 equal to that coutained in it. To j^revent the current from raising the 

 eggs from the bottom of the vessel, the longer branch of the siphon 

 opened out into a little glass saucer floating in the water. In this way 

 the water was continually kept i^ure by the current during the entire 

 process of incubation. Useless organic matter, which rapidly decom- 

 poses in the water, was thus carried off, and the aeration of the water 

 was constant and perfect. (See Plate II.) 



Several comparative experiments have demonstrated the superiority 

 of this system. I think that the eggs should not be deposited on the 

 bottom in too thick layers, and that a depth of water of 15 to 20 centi- 

 meters [6 to 8 inches] is sufficient. 



We made twelve such experiments from July 19 to August 27. The 

 proportion of embryos obtained to the number of eggs used increased 

 from 5 or G per cent to 80 or 90 per cent. These latter results, how- 

 ever, were not obtained till August. 



The duration of the incubation was from five to twelve hours, accord- 

 ing to the temperature. A thermometer plunged into the water showed 

 a variation of 12'^ to 29^. It was noticed that the higher the tempera- 

 ture the more rapid was the incubation and the greater the result. I 

 think it is preferable, however, that the temperature in the vessel 

 should not greatly exceed that of the water in which the embryos are 

 to be planted, so as not to expose them to too great and sudden a 

 change. As soon as there were enough lively embryos in the glass ves- 

 sel they were poured on the collectors as uniformly as possible. 



Only the fecundations which took j)lace in August produced spat ; 

 and they were also the only ones which yielded any considerable result. 

 Ten to fifteen days after the last sexual liquid had been poured into the 

 glass vessel perfectly formed little oysters could be distinguished on the 

 collectors with the naked eye. For some days a decided growth was 

 observed in them. Unibrtunately the precautions taken against an 

 accumulation of mud were not sufficient, and gradually the mud began 

 to cover the collectors and caused the spat to disappear. 



To sum up: The experiments at fecundation made at Pouliguen were 

 perfectly successful, in that (1) we obtained embryos which became 

 fixed to collectors, and began to develop on them; and (2) we have 

 shown the possibility of using as reproducers oysters raised in our 

 country. These experiments will again be taken up next year, and 

 promise a still more complete success, that is to say, the entire devel- 

 opment of the young oysters. 



