49 
0.1 m.? surface") and on soft bottom goes 6—10 cm. down into this. On sandy 
bottom it does not penetrate so deeply; but the numerous experiments made with 
it show, that just as it is most of our waters can be satisfactorily investigated by 
its means. On the other hand, it is difficult to use it on rich Zostera ground, or 
where the bottom is covered with stones or too hard shells, which it cannot crush 
on closing. But such stony grounds are not common on large areas. This appa- 
ratus may be used at as great depths as we wish, but as it must be used many 
times for an exact investigation, the difficulties increase with the depth. In our 
waters, however, with their shallow depths this inconvenience is as a rule not 
met with. 
To examine 100 stations with this apparatus may take a very long time, 
since where there are many dead mollusc shells, these have to be carefully gone 
through in the sieves to find the relatively few living animals among them. Often 
however there is almost nothing but living animals on the bottom and in that 
case, by repeated washing, the bottom-material is removed and 5 samples can be 
taken in the sieves before the animals are counted and preserved; this method has 
been greatly used in the Kattegat and Baltic. In the Limfjord, on the other hand, 
we must as a rule be content with one sample at one time, otherwise the dead 
shells become so numerous in the sieves that it is almost impossible to find the 
living among them. I am not quite clear as to how we are to explain this shell 
richness in the Limfjord; but it is probably connected with the rapid renewal of 
the small, quickly growing molluscs, especially Abra and Solen. 
In the Sound and certain places, especially in Samsø Belt and the south- 
western Kattegat, I have also found large collections of dead molluscs, especially 
Cyprina islandica, Mytilus modiolus and other large forms; they do not grow 
quickly, or at any rate become much older than the small Abra and Solen pellu- 
cidus.. At these places where the bottom as a rule is not soft and where the 
sedimentary deposits are obviously very slight owing to the strong currents, 
the abundance of the shells must probably be explained on the hypothesis, that 
the dead animals of many years lie here on the bottom without being covered by 
sediment. -1 believe that it is in this way, that we must explain for example the 
presence of »Skalen« at Hellebæk. 
The finest sieve has openings of ca. 1.5. mm.?”; naturally many small 
organisms pass through these, Foraminifera, young of molluscs, small worms etc.; 
it would be a quite impracticable work to sort out all these from the often coarse- 
grained bottom-material; these small animals are thus not included in the estimate 
of the quantity of animal life per square unit. I do not believe, however, that 
this error can be very great, and it is certainly of no importance, when it is a 
t) It may be remarked here, that the bottom-sampler does not span over exactly 
0., mZ It was originally constructed to span over a square foot, thus ca. 1346 cm.” but on the 
introduction of the new meter law in 1910 it was made smaller, so as to be as near as possible 
0., m.? It has always been a little larger, however, namely ca. 1160 cm.”; all the data obtained 
by it are thus ca. 16, too large. At the present stage of the preliminary investigations an error 
of ca. ”/,th is however of but small importance. If, however, we wish to compare the results 
with more exact investigations in the future, then this must be taken into consideration. 
7 
