32 
the Chætoceros organisms could not be centrifuged, was proved by centrifuging a 
quantity of Chætoceros taken in the plankton nets and placed in the water. The 
water could not be centrifuged quite clean, it is true, but the main quantity of the 
Chætoceros was nevertheles collected at the bottom of the centrifuging tubes. 
The so-called »nannoplankton«, which passes through the plankton nets 
and which according to Lohmann's investigations plays a considerable role in the 
western Baltic, seems not to have any great importance in the Limfjord according 
to the investigations made up to the present. I have seen extremely little of these 
organisms in the centrifugal experiments I have made. 
5. Origin and quantity of the matter im suspension in the sea at the 
different times of the year. 1 mentioned above a 3rd apparatus for the study of 
the quantity of plankton and detritus, namely, the detritus-collectors. I may now 
briefly discuss the results obtained by means of this apparatus. 
The detritus-collectors give us, as already explained, an expression for the 
quantity of suspended matter, which within a certain period of time sinks down 
through a plane in the water "/,, m.?, situated 30 cm. above the bottom. In the 
course of the year the detritus-collectors have been put out at various places, most 
frequently in Thisted Bredning, once in Nissum Bredning. One difficulty with the 
use of the detritus-collectors is that they are often destroyed by the fishermen. 
We had 3 collectors in the beginning, but of these one was lost in the course of 
the summer. 
The detritus-collectors are taken up at intervals of a half or whole month. 
The greater part of the water is poured off, and the remainder carefully emptied 
out by means of a glass. When but little water remains, the deposit is stirred up 
and the whole.transferred into high glass-tubes, where the deposit is again allowed 
to settle. Then the last portion of the water could be removed, and the deposit 
preserved by the addition of alcohol. On arrival in Copenhagen, the alcohol was 
evaporated, the deposit dried in quite the same manner as the bottom-samples and 
then weighed. In a few cases a determination of the carbon in the deposit 
was made. 
In addition to the weight of the material found in the detritus-collector 
within a certain time, the following table shows how much will be deposited in 
the same time per !/,, m.”, as also how much is deposited daily in the given 
period per 7/4, m.? 
1. Thisted Bredning, 12 meters depth, 1.—15. April 1910. 
1 detritus-collector contained 1.81 gm. 
per "/,, m.? 2.72 gm., per day 0.19 gm. 
2. Thisted Bredning, 12 meters depth, 15.—22. April 1910. 
In 1 detritus-collector 2.35 gm. 
per "/,, m.? 3.54 gm., per day 0.51 gm. 
3. Thisted Bredning, 14 meters depth, 25. April—21. May 1910. 
In 1 detritus-collector 39.8 gm. 
per "/,, m.? 59.2 gm., per day 2.24 gm. 
4. Thisted Bredning, 7 meters depth, 4. June—5. July 1910. 
In 1 detritus-collector 1.47 gm. 
per "/,, m.? 2.2 gm., per day 0.07 gm. 
