182 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



is consequently somevrliat incomplete.'^^ It will, therefore, scarcely be 

 necessary in this place to adduce further proof" of the necessity of soon 

 acquiring such knowledge, which, in the futm^e, will be of great practi- 

 cal use. 



Tlie "herring-food," which is chiefly composed of small crustaceans, 

 depends, as to its occurrence and numbers, on lower and smaller organ- 

 isms, through which it indirectly absorbs all the organizable matter in 

 its neighborhood. Without an exact knowledge of these organisms and 

 the conditions under which they are found we shall never attain to a 

 correct view of the causes x^roducing the "herring-food" and the her- 

 rings. It has long since been known that among these microscopic 

 lower organisms, diatoms occupy a prominent place. On the coast of 

 Bohusliin, especially near Fjellbacka, the fishermen have observed that 

 the tender young herrings generally stay among the greenish "slime," 

 which is chiefly found where fresh-water courses empty into the sea ; and 

 as they had not observed the spawning of the herrings they drew from 

 this the remarkable conclusion that the young herruigs originated from 

 this "slime," chiefly consisting of diatoms. The more frequent occur- 

 rence of diatoms in the mouths of rivers is probably also one of the 

 causes of attraction which draws especially the young herrings thither. 

 In the Christiania fiord Prof. G. 0. Sars has observed a similar organic 

 " slime," c^onsisting chiefly of diatoms, in great quantities, early in spring 

 or immediately after the breaking of the ice; and in the open Skag- 

 erack I, myself, whilst examining the so-called " Koster Grounds" during 

 the summer of 1871, found large numbers of diatoms in the current 

 going along the outer coast of Bohusliin.''^ In the Polar seas Scoreshy 

 has already observed large numbers of diatoms, and his observations 

 have been corroborated by the Swedish Arctic expeditions. The ceno- 

 bitical and practical importance of the diatoms, as well as their develop- 

 ment from a "formless organic slime" ("free indefinite protoplasm," 

 "formless indefinite organic matter") has recently been discussed by 

 Prof. Youle Hind and Prof. G. 0. Sars. As this "sea-slime" chiefly oc- 

 curs in the Polar seas, especially where there is Polar ice, and is by the 

 currents driven farther south. Professor Sars very beautifully remarks 

 that "in the inhospitable Polar Sea, filled with ice, we find the last 

 causes of the inexhaustible wealth of the more temperate seas." The 

 influence of the Polar regions and the Polar ice on the herring-fisheries 



■•^Prof. K. Moehius, of Kiel, a member of the commissiou appointed to investigate flie 

 Gennan seas, sajs very truly : "We are still woefully ignorant regarding the physical 

 conditions of a cenobitic region and their relation to the plants and animals of such a 

 region, as also regarding the mutual influence of the plants anil animals existing 

 there at one and the same time. So far we kuow but very little regarding the ceno- 

 bitic life of the different and distant regions of land and water." — ZclUchrlft fiir tcis- 

 semclMj'tllche Zoologie, XXX. Supplement, p. 376. 



''•'As even at that tinte I was convinced of the importance to the fisheries of these 

 microscopic organisms, I have repeatedly pointed to the necessity of making them an 

 object of special scientific investigations. 



