[33] THE OYSTER AND OYSTER-CULTURE. 715 
were then leased, generally for a long term of years. From time to time 
the government caused the banks to be officially examined, in order to 
find out their condition and prevent their depletion by overfishing. The 
examination was conducted by commissioners appointed by the govern- 
ment, and the dredging carried on in their presence was performed 
by fishermen specially sworn for the purpose. The smaller beds were 
dredged in three, the larger in six, different places, and all the oysters taken 
were divided, according to size and age, into three classes, known as— 
1. Zahlbar Gut, or marketable. 
2. Junggut, or medium (half grown). 
3. Junger Anwachs, or young growth. 
The marketable oysters are those which are large and full grown. Their 
shell is at least 7 to 9 centimeters in length and breadth, and when 
closed the greatest thickness must be more than 18 millimeters. The left 
valve, or the one which is most curved, is from 6 to 9 millimeters thick at 
the point of attachment of the shell-muscle, and also under the ligament. 
The greater number of full-grown oysters are from seven to ten years 
of age, yet many older ones are found, which can be distinguished from 
the younger ones by the greater thickness of their shell. Oysters more 
than twenty years old are seldom seen. The oldest which I have per- 
sonally examined I estimated to be from twenty-five to thirty years old. 
The left valve, at the muscular impression and below the ligament, was 
20 to 25 millimeters in thickness. ; 
The shells of the half-grown oysters, when closed, show a thickness 
of from 16 to 18 millimeters. The valves, where thickest, are, at the 
most, only 5 millimeters thick, and their breadth is less than 9 centi- 
meters. They are cleaner than the old oysters, upon whose shells are 
generally to be found many animals and dlants. The young growth are 
those small and thin oysters which are not older than from one to two 
years (Fig. 8 d). 
In the record of each inspection we find indicated the number of n.ar- 
ketable and the number of medium oysters caught in each haul of the 
dredge, but the number of the young growth is not given, mention only 
being made as to whether there were many or few.* 
them to be taken in that place. We except, however, those who take them in our 
name by the authority of our liege at Ribe. Whoever shall dare to act contrary to 
this command, and he can be justly convicted of so doing, shall be punished accord- 
ing to his deserts. Each one is then to govern himself accordingly, and guard against 
transgressing. Given at Skanderborg, the 4th day of February, 1587.” 
* The work of Kréyer contains also a tabular review of the numbers of mature and 
medium oysters of the official investigations which took place from 1709 to 1830. This 
table, and also tables for which I have to thank the royal government at Schleswig, 
have furnished me the numbers from which I have estimated the proportions between 
half and full grown oysters. I have not considered the investigations previous to the 
year 1730, partly because in the beginning of the eighteenth century a number of beds 
were unknown, and partly because the numbers of the first five inspections (1709 to 
1728) give no positive results. On six official investigations made between the years 
1869 to 1876 I have participated myself. The results of these I will give later. 
