33 
as complete proof that the small oysters are more numerous on the shallow grounds 
than in the deep water. 
Å glance at the Tables I—III shows at once, that most of the oysters 
taken wereeither large ca. 2"/,—4 inches (ca. 6—10 cm.) in diameter, or quite 
small under or about 1 inch. We exclude here the young of the year (0-group), 
which in the autumn are often so extremely numerous and can then as a rule 
be easily separated from the older by their small size, 1/, inch or less. 
In the spring we usually meet with a group of small oysters of !/,—1 
inch on an average, hut it is far from being so numerous as the 0-group was in 
the autumn, and I believe that this group consists of the young oysters of both 
the preceding years; these small oysters namely grow so differently that I have 
been unable to separate them hy exact measurements. Their reduction in number 
is due to the death-rate caused both by the winter cold and the attacks of enemies. 
If we can thus not even separate the 0 and I groups longer than for a few months 
in the autumn, it is obviously hopeless to search after the subsequent groups 2 
and 3 etc. The remarkable minimum at ca. 2 inches (or ca. 4—5 cm.), found in 
almost all the measurements, may probably have its explanation in that many 
small oysters die, and those at ca. 2 inches grow so quickly that they soon join 
on to the adult group (6—10 cm.). This minimum does not move either in the 
course of the year (see Tab. IIM), but may be different on different banks, accor- 
ding as the oysters are larger or smaller on an average. Thus, it is higher in 
the large oysters dredged at Volstrup (see Table III) than in those pole-dredged 
there in the neighbourhood (Table III). Concerning the age and growth of the oyster 
the measurement method can therefore only show, that an oyster of ca. 6—7 cm. 
is as a rule 3 summers old, and that the oyster begins to grow more slowly 
in length at 6—7 cm. This is of the greatest importance in the determination 
of the minimum standard size, concerning which more mention will be made later. 
By marking oysters, if we could only find a practical method, we might 
be able to follow the growth at the different places and under different conditions 
with great exactness; this must be tested in the future. If it should be done, it 
would .certainly prove that the oysters grow very variously under different con- 
ditions, thus for example in the youngest group (0-group) according as it is fixed 
on collectors in shallow water or on the deeper banks. 
That the oysters when older do not become very large in shallow water, 
is shown distinctly in Table III, where all the oysters pole-dredged from April 1906 
to August of the same year have apparently not grown in the least: most of the 
adult group are at 7—8 cm. the whole time, and in the previous year 1905 (see 
the Table No. 4) they had quite the same size; but unfortunately there was but 
little fishing m 1905. These pole-dredged oysters are almost all under-sized accor- 
ding to the present conditions of the contracts, as the rectangular standard now 
used of 8 cm. in breadth and. 3 cm. in height permits all flat oysters of 
8 cm., to pass through as undersized and even many at 9 cm.; only 2å of 
all the pole-dredged oysters (those at 10 cm.) are therefore certain to he 
considered as standard oysters. It appears as if these oysters in the shallow water 
(8—4—5 feet) never become standards, and they are so situated that a severe 
winter, it is to be feared, will kill them, if they do not die earlier from old age or 
