214 THE POPULAR SCIENCE MONTHLY. 



the sea seeming to be essential to the ripening of the ova a property 

 which makes the study of the procreative functions of this tish moi-e 

 difficult. The tunny lives exclusively in the sea, but goes to the coasts 

 of the Mediterranean, particularly to Sicily and Sardinia, to spawn. 

 The sea graylings ascend the rivers of Spain and France in such num- 

 bers that the water seems covered with them. 



The journeys of the fish in returning from their spawning-places 

 after spawning are seldom performed in masses, but individually and 

 in small groups. The fish, which went up fat and in fine condition 

 and flavor, are exhausted, lean, and weak. Not much is known of the 

 migrations of other fish than the salmon during these journeys, for the 

 fishermen pay little attention to them and they therefore seldom come 

 under the observation of science. 



Xext in order of the migrations are those of the young brood from 

 their spawning-places. The young herring do not as a rule remain 

 longer than four or five months where they are hatched. They then go 

 down to the sea while the young eels go from the sea up to the rivers 

 after about the same time. The young herring are observed with diffi- 

 culty, for it requires a skilled eye to perceive their minute, transparent 

 bodies in water that is in any degree disturbed ; but in j^erfectly still 

 water the schools may be seen moving to and fro like fine flecks of 

 cloud. The salmon remain a full year in the mountain-streams, and 

 do not go down to the sea till they have become a vigorous, greedy 

 fish of about a finger's length. 



Journeys in search of food ai'e not periodical or regular, like the 

 previous migrations, or are only incidentally so. The most important 

 of them and the nearest to being jjeriodical are the visits of the codfish 

 to Newfoundland and the Loifoden Islands, concerning which it is as 

 yet not certain whether they may not be partly connected with pur- 

 poses of reproduction. Schools of other smaller fishes appear along 

 with the cod, a salmonid, the herring, and a number of squids, which 

 are all alike used by the fisherman as bait. The migrations of the 

 predatory fish which follow the other fish in their spawning-journeys 

 naturally partake of the periodical character of those journeys ; the 

 fish that pursue the herring follow them into the farthermost corners 

 of the bays to which they resort. 



The autumnal visits of mackerel to the Gulf of Kiel are of particu- 

 lar interest. They do not take place every year, and are not often 

 marked by very great numbers, but they have attracted attention since 

 1624, when they were described by Schonevelde, on account of the 

 peculiar character of the food that attracts the fish. The Gulf of Kiel 

 is visited in August and September by great numbers of the Medusa 

 aitrita, which fill its waters, perform their reproductive duties, and 

 perish on its shores, leaving hardly a trace of their watery tissues be- 

 hind. In their maws swarm numerous individuals of a moderately 

 large parasitic crab, and it is for the sake of these that the mackerel 



