564 NATURAL HISTORY OF AQUATIC ANIMALS. 



recently, however, oiie important element of their biography has been unsolved, namely, the 

 precise nature of the i'ood upon which they .subsist, at least during the time when they come 

 into the vicinity of the shore, although their varying degree of excellence throughout the year 

 is believed to depend largely upon what they lincl to eat in the different months. 



" Intimately connected with this same subject of the food of the Herring is the fact that 

 at times it is found almost impossible to preserve the fish after being caught, since, notwith- 

 standing the prompt use of salt, decomposition ensues and spoils the entire catch. Indeed, 

 at certain seasons of the year, it is said that Herrings cannot be preserved at all except by 

 taking the precaution of retaining them alive in the net for a period of from three to ten days. 



"A very important communication on the food of the, Herring has lately been published 

 by a Danish author, Mr. Axel Boeck, from which we learn that the herring food, or ' meat,' con- 

 sisting almost entirely of iniuute invertebrate animals, is divided by the northern fishermen into 

 three classes; the 'red,' the 'yellow,' and the 'black,' the names being derived from the color of 

 this food when living, or else from its appearance when in the fish's stomach. The red meat 

 (Rodaat) is the most common and best known, and occurs along the entire coast of Norway and in 

 the mouths of the bays (but more sparingly in the bays themselves), and in the open sea, dimin- 

 ishing in amount, apparently, with the depth. At certain periods of summer, however, it appears 

 in such immense abundance that the sea is colored red by it. When floating in this way upon the 

 surface, it attracts innumerable schools of mackerel, as well as of Herrings, which are then much 

 less shy than usual, and the scene is one of impressive activity, owing to the number of boats 

 and nets employed in fishing. On a careful examination this substance was found to consist 

 almost entirely of small crustaceans, Copepod, the largest, scarcely the thirtieth of an inch in 

 length and barely distinguishable by the naked eye. 



"It can hardly be believed that such minute and almost microscopic animals can be of 

 so much importance to the welfare of a nation ; but in reality the mackerel and the autumnal 

 Herrings owe their fatness to them, the microscope revealing through their thin shells the fat 

 lying in distinct strips between the muscles and intestines. 



"These same crustaceans occur also off Spitsbergen in such abundance as to furnish food 

 to innumerable water fowl; and even the whales feed upon them to a great extent. 



"If, now, the Herring has taken in a large quantity of this 'red food,' and is then cap- 

 tured and killed without its having been fully digested, the animal matter in the stomach 

 of the fish begins to spoil before it can be reached by the salt, and the stomach thus becomes 

 putrid, as well as the large bloodvessel which lies under the back, the coloring matter of 

 the blood imparting a reddish tinge to the flesh alongthe backbone. For this reason it is 

 required by law to keep Herrings three days in the nets, in order that all the contents of 

 the stomach may be completely digested, while the -fish is prevented from taking in a fresh 

 supply. Sometimes, however, the winds drift this herring food into the nets, and furnish to 

 the Herrings an opportunity, which they eagerly embrace, rendering them again liable to the 

 difficulty just mentioned. 



" When a Herring, on being squeezed, discharges a yellow pulp, this is known as ' yellow 

 meat,' or Gulaat. This is not so abundant as the other, but appears, like the 'red meat,' to 

 be composed in part of transparent Copepods, together with the larvaj of tapeworms and other 

 annelids which occur on the Norwegian coast in immense numbers. It is stated that the 

 surface of the sea is sometimes seen to be. completely covered with little worms of about the 

 twenty -fourth of an inch in length, swimming actively about by means of certain hairs which 

 encircle their bodies like a girdle. These animals were sufficiently developed to permit their 



