OYSTER CULTURE IN AMERICA. 825 



It is necessary, then, having accepted the theory, to 

 determine what proportion of the oysters should be taken 

 off the beds, and what proportion is actually removed. As 

 there is no data to my knowledge, derived from observations 

 made in this country, to determine the first of these two 

 desired points, it is necessary to turn to the experience of 

 foreign oyster fisheries for guidance ; and though the 

 animals and the conditions under which they live are not 

 entirely similar, yet some information may be obtained 

 and a line of investigation marked out for the future. 



The following is a synopsis of the deductions of (the 

 late) Professor Karl Mobius, professor of zoology in the 

 University of Kiel, whose work, in manuscript, on the 

 oyster was kindly lent me by Professor Baircl. The obser- 

 vations were made over the Schleswig-Holstein oyster-beds 

 by government officials, from 1730 to 1852, and were car- 

 ried on in, practically, the following manner : Each bed 

 was dredged over in three or six places, according to its 

 size, and the oysters taken were divided into three classes, 

 and carefully counted. 



The classes were denominated "marketable," "medium," 

 and " young growth." The " marketable " oysters were full 

 grown and mature, from 7 to 9 centimeters in length and 

 breadth, and 18 millimeters thick. The " medium " were 

 half-grown oysters, from 16 to 18 millimeters thick and of 

 less than 9 centimeters in breadth. The " young growth" 

 were those one or two years old. From these observations 

 Professor Mobius discovers that there was an average of 

 42 1 medium oysters to i ooo full grown ones. The average 

 of all the observations differs very little from the number 

 given by each, and consequently shows that there was but 

 slight fluctuation in the proportion in one hundred and 

 twenty-two years. The medium oysters are considered by 



