BULLETIN OF THE UNITED SPATES FISH COMMISSION. 321 



more active, transport themselves into the living - waters to there take 

 up the nutritive matters which are necessary to transform them into 



spat. 



HYBRIDIZATION. 



There are, therefore, great differences between the Portuguese and 

 common oyster of our coasts, not only from a couchological pointof view — 

 that is to say, in respect of external form — but also as regards their 

 malacological and embryological peculiarities. The characters of each 

 are so well marked that the question of hybridization, which has so 

 alarmed our maritime population, would not have needed to be raised. 

 We understand that, according to a preconceived theory of certain cul- 

 turists, these two rival species of oysters are susceptible of crossing. 



The Portuguese, on the one hand, tending to abase the purity of our 

 race of oysters; on the other, on account of its fecundity and vitality to 

 replace the common oyster, to invade our banks, to ruin our propagat- 

 ing parks. This prediction has happily not been realized, and our oys- 

 ters, also those of Arcachon, those with the fine and nacreous shells of 

 some of the rivers of Bretagne, the green oysters of Mareunes, the deep- 

 water oysters grown on the sands of d'Olonne, have lost nothing of their 

 purity and primitive qualities. We consider it useless in this place to 

 state the weighty reasons which impel us to combat this theory. 



We would simply remark in this place that it is now nearly thirty 

 years since the Portuguese oyster has been introduced into the w T aters of 

 Arcachon. If they have exercised the influence which has been sup- 

 posed upon the native oysters of the basin, we cannot find any evidence 

 at this ostracultural station of a single individual which shows the effect 

 of hybridization. N 



On the other hand, not a single bed can be cited where they have 

 caused ruin and diminution of fertility. Have they injured the oysters 

 of Arcachon? The marshes not transformed into parks; the canals of 

 the basin, are they less productive than in times past? The banks of 

 Brittany, still so rich (the Portuguese- oysters have been cultivated in the 

 rivers of Auray and La Trinite), have they suffered in the least? Does 

 the dredger of to-day encounter many Portuguese or hybrid oysters? 

 Xo. These fears, we repeat, are not justified, and this for the reason 

 already stated, that the two rival bivalves live and are adapted to en- 

 tirely different environments. Moreover, the following experiments 

 demonstrate scientifically the inanity of the doctrine of hybridization. 



The surest means of discovering if cross-fertilization would take place 

 consisted in bringing into contact the generative elements of the two 

 species participating, or supposed to, in this act. It is in this way also 

 that we should proceed when we would learn if the individuals of allied 

 species <>r varieties of the same species are susceptible of concurring in 

 the production of a being. Very often, when closely allied species or 

 varieties of the same species were used, the cross-fertilization would 

 not end in the production of living embryos. The elements soinetiine*s 



Bull. U. S. P. C, 82 21 April 19, 1883. 



