6 12 OYSTERS, AND ALL ABOUT THEM. 



The Portuguese Oyster. 



The mollusc known under the name of the Portuguese 

 oyster did not exist on our coasts 30 years ago. The 

 Delessert Museum (Lamark Collection) contained the only 

 specimen we had. Its introduction and acclimatisation are 

 due to an entirely accidental cause. 



The natural history of this oyster was little known, 

 and there were but very vague ideas with regard to it. It 

 was supposed to be similar to the ordinary oyster, from 

 which, however, it differs : i, in form; 2, in flavour; 3, in 

 habits ; 4, in sexuality. 



It is superfluous to describe its external appearance, 

 which has no resemblance to that of the ostrea edulis. 



As regards the taste and flavour, even the least culti- 

 vated palate can perceive the difference. As regards its 

 habits, we know that it delights in brackish and muddy 

 waters, and multiplies in them in preference to every other 

 locality. It is found, in fact, in the Gironde, on the coasts 

 of Oleron, and at the mouth of the Charente, where the 

 water weighs by the areometer from i to 3 degrees. 



It also breeds in the basin of Arcachon, but to no 

 extent, and only at those points where the influence of 

 fresh water is felt. In this locality a rather curious pheno- 

 menon may be observed, viz., that the Tagus oyster becomes 

 unfertile after a certain time, so that it would entirely dis- 

 appear from the basin but for the continual introduction of 

 fresh specimens, which perpetuate the species. 



As regards the sexuality, there is a greater and more 

 radical difference between the two species of testacea. 

 The ostrea edulis is hermaphrodite ; the ostrea angulata is 

 unisex, or of two genders. We have opened more than 

 10,000, in every phase of the reproductive period, and 



