236 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



sons, and we must confess that we have not escaped the seductions of 

 this idea.* 



In June, 1880, we arranged in the laboratory of M. Balbiani, at the 

 College of France, a contrivance destined for the artificial incubation 

 of oyster eggs and the fixation of embryos, composed of a series of tubs 

 through which a constant current of filtered and aerated sea- water circu- 

 lated. (See Plates III and IV.) Eggs in every stage of development 

 and embryos of every age were placed, eajch separately, in the difierent 

 apparatuses. A layer of fine sand, placed towards the outflow of each 

 tub, permitted the water to flow out easily, while the young oysters and 

 eggs remained safely inside, it being impossible for them to escape. 



Tlie oysters from which the subjects for our experiments had been 

 drawn came partly from Arcaclion and partly from Brittany, and arrived 

 in a perfect state of preservation and freshness. The following took 

 place : Some hours after they had been extracted from the mantle of the 

 mother oyster, and had been jilaced in one of the incubating boxes, the 

 eggs which were at the point of splitting ceased to develop and com- 

 menced to decay. Embryos in the condition of white spawn, although 

 very lively when placed in the water, became motionless, and died after 

 three or four days, according to their degree of develoi^ment; while 



'' As regards collectors, wo have heard a man who is exceedingly competent and 

 tlioronghly conversant with all matters pertaining to oyster cnlturo advance a theory, 

 which we deem proper to report without, however, passing any opinion as to its value: 

 Is it indispensahle for the young oyster to attach itself to some object in order to live 

 and grow? When it is in its natural state there is not the slightest doubt in this 

 respect. Tlie currents to which the embryo is exposed compel it to attach itself to 

 some object, if it is not to be buried in the mud or tossed about, iujured, orsuflbcated 

 by the waves. But under certain conditions, on a suitable bottom, on sand free from 

 sediutcut, where very pure water circulates slowly, would it not bo possible for the 

 young oyster to develop without an object to which it is iixed, which object under all 

 circumstances is only of temporary use, because it may, with impunity, be removed from 

 it a few days after it has become fixed ? At the time Ayhen the spawn is black the em- 

 bryo is nearly perfect. Some may be seen whose ciliary apparatus is so much reduced 

 that they can hardly move. Their two valves, however, work woll; in short, they 

 difl'er from an adult oyster only by their small size and the convexity of their shells. 



At the agricultui'al exposition of Edinburgh an oyster cultivator exhibited small 

 oysters which appeared independent ; but he did not tell how he obtained them, nor 

 could he prove that they would bo able to raise themselves. Possibly they were only 

 embryos in an advanced stage of development. 



In this connection we will relate a circumstance which occurred at a reservoir of 

 M. L<Son Lcsca, counselor-general of the Giroude, and owner of iisli ponds on the 

 banks of the Arcachou basin. Four years ago ]^r. Lesca observed in one of his reser- 

 voirs small oysters which a])pearcd to have been deposited on, ratber than attached 

 to, tlic gravel and broken pieces of algre at the bottom of the pond. This discovery 

 was not without interest, as spawn of oysters had never been seen in that pond. Tho 

 oysters were allowed to grow freely, without giving them tho least care, iu order to 

 see what would become of theui. Mr. Lesca has recently sent us some specimens of 

 tiii'so oysterw, which luxd leached an average size of '.) to 12 centimeters [ahout 4 

 inches], and in several of them we noticed that there was no xilacc for attachment ; or, 

 at any rate, it was not visible. 



