M. Kroyer on the Danish Oyster'Banks. 23 



required in a statistical inquiry of this kind, although certainly 

 they open up no very agreeable prospect for the revenue or fdr 

 the lovers of oysters. But let us now direct our attention to 

 the separate portions of the treatise, in so far as they are suited 

 to our objects. 



The first part, which is dedicated to the natural history of 

 the oyster, contains, besides much that is already known, also 

 much that is new, by which previous statements are enlarged, 

 restricted, and partly corrected. In the Jutland oysters, the 

 author found six pearls, two of which were of the size of pead, 

 and the others of small shot ; but, generally speaking, they 

 are rare, and of small dimensions. In the oyster-banks of 

 Schloswig, the Ostrea hippopits occurs ahmg with the Ostrea 

 edulis ; but, as its taste is inferior, it is of inferior value as an 

 article of trade. There is no new information respecting the 

 organs of generation. Kegarding the period of propagation, it 

 resulted from the investigations of the author, that it does not 

 appear to take place simultaneously. He found, in July and 

 August, individuals which, on opening the shell, contained a 

 milky fluid, which exhibited, under the microscope, very mi- 

 nute but perfectly formed young ones, provided with a thin 

 shell ; but such oysters were rare, for hardly one was met with 

 in ten. The opinion, that oysters, at the period of their propa- 

 gation, are lean and of a bad watery taste, is fully proved to be 

 erroneous ; when newly taken out of the sea, their taste is just 

 as good in summer as in winter ; and there is no foundation for 

 the belief that the eating oysters in summer is unhealthy. The 

 statement, that oysters only live in such places as are never 

 uncovered during the greatest ebb of the tide, is limited by 

 the author. In northern districts, they cannot endure the cold 

 at low water, and hence they live at a greater depth. But 

 several of the oyster-banks of Schleswig have so low an amount 

 of water, that they are bare during a great ebb, or during cer- 

 tain winds. The author has ascertained similar facts on the 

 Norwegian coast. On the west coast of Schleswig, it has often 

 been remarked, that, in summer, oysters occupy spots which 

 are even frequently laid bare, and that the oysters in- these 

 places can thrive a considerable time when the winters are 

 mild ; but if a frost take place, they speedily succumb. An 



