50 
question especially of determining the amount of fish-food present; the fishes do 
not take such small organisms, simply because they cannot see them. 
The 0.1 m.? bottom-sampler, as I use it, has already passed through a long 
development and this is not yet ended; small improvements are constantly being 
made in the apparatus. I have not thought it necessary or right, therefore, to 
give detailed drawings of it, as it cannot well be constructed from them in any 
case. The accompanying photographs however give in the main a correct represen- 
tation of the apparatus and its mode of working. 

VII. Methods for the determination of the mass of animal life. 
With the help of the bottom-sampler, and the sifting and counting of the 
individuals of each single species in each sample, we obtain, as is shown in the 
accompanying charts and tables, an enumeration of the animals living on the square 
unit of area; but the individuals of the same species are not equally large, so that 
the mass of the single species is but badly represented by the number of indi- 
viduals. Weighing of the individuals collected is quite necessary in order to 
obtain a more correct representation of their mass at each place. To obtain a view 
over the whole of the organic material present at a place, therefore, all species 
must be weighed. The rough weight of the animals, somewhat freed of water, 
already gives something. The molluses are made to open by covering them with 
warm water, so that they let the water between the shells run out; but the otber 
animals are weighed just as they are, though often washed with freshwater, after 
being rolled in blotting-paper, so as to be somewhat dry. The rough weight given 
in the tables has been determined in this way. 
But it did not seem satisfactory to stop at the rough weight alone; on the 
one hand, the different animals contain different quantities of water, on the other 
some have such an enormous amount of calcareous matter in their shells or 
skeletons, that the weight of this quite dominates the amount of the true orga- 
nic matter. 
On the proposal of Boysen Jensen we then took up the determination 
of the amount of organic dry matter in the animals; regarding the methods he 
gives the following information. 
After that the bottom-samples were passed through the sieves, as described 
above, the animals were either, after being weighed, preserved in alcohol, each 
species separately, or all the animals from a definite locality were, without being 
weighed, thrown together into one glass and covered with alcohol. The deter- 
mination of the organic dry matter in the animals was carried out somewhat 
differently, according as the one or the other of these methods was used. 
