884. 



OYSTERS, AND ALL ABOUT THEM. 



thirty years old. The left valve, at the muscular impression 

 and below the ligament, was 20 to 25 millimeters in thick- 

 ness. 



. During the period from 1730 to 1852, ten 

 records were made of all the oyster-beds of the Schleswig- 

 Holstein sea-flats. If from these records the numbers of 

 all the marketable and all the medium-sized oysters are 

 taken and added together, we will have a series of very 

 different totals, showing no particular general law. But if 

 for each of these reports the proportion of marketable to 

 medium oysters is taken, then we will arrive at the sur- 

 prising result that this proportion fluctuates but very 

 slightly during all the records. 



The following table gives a summary of the market- 

 able and medium oysters recorded as caught during each 

 of the ten investigations. From these numbers I have 

 reckoned for each record the proportion of medium oysters 

 to every thousand of those which were full grown. 



