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BULLETIN OF THE UNITED STATES FISIT COMMISSION. 235 



Feariug- tliut tbc trepauuinj!: oporatiou niiglit have distiirbod the 

 j^euerative functions of tlie oysters wo made another experiment which 

 entirely confirmed the former, in tlie very beginning of tbc season, 

 towards the end of April, we selected some oysters in which we had 

 observed spawn, and placed them separately in a very fine bed where 

 they would find all the conditions for reproduction in the greatest per- 

 fection. AVlien oiKiiied in September, at the time when the last breeders 

 emitted their embryos, cuts made in their full glands proved conclu- 

 sively that they could not have spawned again before the following 

 spring. 



There remains the supposition that there is an annual spawning sea- 

 sou in several successive emissions. It is possible and probable that 

 ovulation is not accomplished at one time and in a single day, but it 

 cannot be supposed that there is an interval of several months between 

 the emissions, like that between the period of June and the period of 

 September. We have, moreover, noticed that when, in an oyster en- 

 gaged in the process of gestation, the eggs remained in the oviducts 

 tbey were invariably damaged or sickly. It appears to us, therefore, 

 that one spawning per season is the rule in the common oyster, as well 

 as in the Portuguese oyster, and that any variations from this rule are 

 anomalies, like oysters spawning in December or January.* 



The idea of keeping and raising in close waters the embryos of the 

 oyster, and to find them later on the collectors, has tempted many per- 



*As "wfi deemed tbo trepauning process referred to above eminently suitable for 

 facilitating tbc study of certain questions of natural history, some of wbicb concern 

 directly tbe science and industry of oyster culture, we consider it proper to add some 

 details to tbe information already furnisbed. 



Tbe fact of making an opening, even comparatively large— tbe trepan wbicb we 

 used measured not less tban 1^ centimeters [over one-balf incb] in diameter — in tbe 

 valves of au oyster does in no wise endanger its life. It is advisable, however, to 

 Avork tbe trepan with caution when tbe perforating process approaches its end, so as 

 not to injure tbe animal. A slight wound, however, will heal very quickly. After 

 tbo hole has been made, and tbe little pieces of shell which have fallen into it have 

 been removed, it becomes necessary to stop up tbe opening as firmly as possible, eitber 

 Avith a piece of cork, wax, or some other substance. 



'I'he closing up of tlic hole is to prevent lice, small crustaceans, &c., from penetrating 

 into tbe shell, or attacking the animal at a defenseless point, and also to prevent the 

 water from entering the sbell. If the oyster which has been thus operated upon is 

 placed in a good park, and if it is in a period of vigorous growth, the cicatrization, or 

 the restoration of the shell, is accomplished within a Aveek. It is not absolutely com- 

 plete, but tbe animal has covered the cork with a thin shell of mother-of-i^earl, wbicii 

 protects it against outside enemies. In some oysters which we observed aa'c could 

 only counteract the too rapid formation of this mother-of-pearl by turning the cork 

 several times every two or three days. 



In this manner we have made as many as five holes in tbe shells of French and 

 Portuguese oysters, and they bad been so little hurt by the operation that they were 

 exhibited last year at tbe Bordeaux Exposition, and still bore on their shells tbe 

 marks caused by our experiments. 



