68 
great rarity, at least in these years. I have been much astonished to see, how 
the young Mya have decreased in numbers in Thisted from 1909 to 1910 (see 
Table V), but the numbers of the adults increased in the same time. Can this be 
the result of the great transplantation of plaice which began in 1908? If so, then 
Mya will eventually die out here, perhaps the process is going on now; possibly 
it is just the persecution of the young individuals by the plaice, which has led to 
scarcity of Mya in the western reaches and Sallingsund; here there is always a 
large and abundant stock of plaice. It will be of interest to follow the further 
development of this matter in subsequent years; Mya will possibly become rare in 
Thisted, as it is now in Kaas and Sallingsund, and other Lamellibranchs such as 
Solen and Abra will take its place, which they seem to be able to do on account 
of their numbers and rapid growth; the annual production of plaice on these 2 
last-mentioned areas is namely much greater per m.? than on the areas where 
plaice are inplanted; the plaice it is true do not grow so rapidly here as in Thi- 
sted, but the stock of them is much denser. 
Whilst therefore we can make an endeavour to determine approximately 
the consumption of food by fishes at several places in the Limfjord, we are quite 
helpless, as said, in regard to the determination of the consumption of 
the whelks and starfish; in consideration of the great mass of these animals 
this consumption must probably be great, perhaps greater than that of the 
fishes; their total mass of dry matter was indeed ca. 5 times larger than that of 
the latter. If we place the consumption of these animals at twice that of the 
fishes, thus ca. 60 gm. per 10 m.” we obtain 
Consumption of the: fishess.. 222: ca. 30 gm. dry matter per 10 m.? 
Consumption of whelks and Åsterias .. ca. 60 -  - — MERE 
What is further produced as increase in the course of the year, including 
here the increment for Mya, ca. 200 gm. dry matter per 10 m.”, must be added 
as provisional excess, in order to obtain the total production of dry matter per 
m.? This would be therefore, at the lowest estimate, about 300 gm. or 30 gm. 
per m.? In Thisted Bredning the total quantity of the dry matter of the bottom- 
fauna per m.? was somewhat similar. 
The fauna living on the bottom would thus as a whole reproduce 
its own mass each year; some species are known to do this several times over 
(bra), others probably cannot do so; the main result seems therefore not improbable. 
I do not lay exceedingly great weight, as mentioned, on these preliminary 
results; but in order to carry the principle of metabolism as far as possible, we 
must also endeavour to understand, on what materials and what quantities 
this bottom-fauna is nourished. The dry matter of the bottom-fauna per m.? 
was ca. 30 gm.; if we reflect now on its comparatively rapid growth, we may well 
assume that, like the fishes, it consumes its own weight several times yearly; it 
must therefore use up a quantity of organic matter which is several times larger; 
and we must remember here that the shells of the large animals and the chalk of 
the Echinoderms are not included in the quantity of dry matter. This quantity of 
food is obtained by the bottom-animals, as already mentioned, mainly from the 
everywhere present, dust-fine detritus, the origin of which is due in the first place 
to the bottom-flora. No measure can yet be given of the annual production of 
