86 Prof. K. Mobius on the 



A great quantity of uniform nourishment in a region is 

 therefore favourable to the growth and fertility of fishes ; and 

 it is this that collects the fishes in particular places in such 

 quantities that a profitable fishery can be carried on there. 



The value which great quantities of animals of the same 

 species may attain as fish-nourishment may be shown by an 

 example. The oldest fishermen of Ellerbeck can number no 

 year in which they took so many herrings in Kiel harbour as 

 in the winter and spring of 1872. According to the estimates 

 of MM. F. Holm and J. Schmidt, fish-dealers of Kiel, for 

 three weeks, especially in January and February, 3000 walls 

 of herrings (mixed with sprats) were taken daily. Each wall 

 consists of 80 fishes. The contents of the stomachs of the 

 herrings captured consisted chiefly of a small crustacean, 

 Temora longicornis, the fore body of which is only 1 millim. 

 in length. Here and there among them there was another 

 equally small Copepod, Dias longiremis. Very rarely some 

 larger Crustacea (Mysis Jlexuosa, Idotea tricuspidata, or Gam- 

 marus locusta) were intermixed with the food. Very often 

 nothing but Temora longicornis was to be observed in five or 

 six samples of the contents of the stomach when examined 

 microscopically. These little crustacea filled the stomachs of 

 the herrings as a stiff paste of a pale reddish colour ; in the 

 intestines there was a soft red excrement, in which the legs, 

 antenna;, and spermatophora [egg-sacs ?] of the same Copepod 

 were still recognizable. On the 28th of February I took from 

 the stomach of a female herring, of 25 centims. length, 1*5 

 cubic centim. of the above-mentioned stiff Tkraora-paste, and 

 placed it in spirits, in order to undertake subsequently an 

 estimate of the number of animals eaten. The whole volume 

 of the mass diluted with spirits amounted to 9 cubic centims. 

 It was shaken up in the bottle in order to diffuse the crusta- 

 ceans equally, and 1 cubic centim. of it was taken out. By 

 counting this in portions I found in it 2130 specimens of 

 Temora longicornis ; this number multiplied by 9 gives 19,170 

 Copepods in the contents of the stomach, consisting of 1*5 

 cubic centim. of jPemora-paste. This gives 12,780 specimens 

 to 1 cubic centim. of the contents of the stomach. 



A female herring, with a particularly full stomach, opened 

 on the 24th of February, contained 4 cubic centims. of 

 jTemora-paste, three specimens of Mysisjlexuosa, and one Idotea 

 tricuspidata. The Teniora-Tp&ste was diluted with spirit until 

 the whole mass made 19 cubic centims. Of this 1 cubic 

 centim. was poured off after the Copepods had been uniformly 

 diffused by shaking the bottle. At my request, Dr. Biitschli 

 counted the animals existing in it and found 3205 specimens. 



