504 POPULAR SCIENCE MONTHLY. 



salmon, gave Miescher peculiar opportunities for this investigation. 

 The salmon spawn during the latter half of November and the early 

 part of December, or just before the shallows of the lakes and streams, 

 where the eggs are deposited, are frozen over. These eggs are hatched 

 by the warmth of the next spring. During the following year the 

 young salmon live in the lakes and streams, and when a year old and 

 from seven to nine centimeters in length swim down the river and out 

 to sea. These facts were easily established. To determine the probable 

 period of the salmons' return to fresh water was more difficult. By 

 measurements of more than two thousand of the fish caught at Basel, 

 together with statistics of those taken in the lower reaches of the Ehine 

 and in other rivers of Germany and Sweden, Miescher found that the 

 greater number both of males and females could be classed under one or 

 other of three sizes. Contrary to what might have been expected the 

 most numerous of these classes is that of the largest and oldest fish, 

 while the least numerous is that of the small 'St. Jacobs' salmon. 

 Unless it be supposed that some of the younger fish go to other rivers, 

 which is unlikely, it is evident that not all the salmon of the proper 

 age participate in every migration to fresh water. These considerations 

 and others, based on the probable rate of growth of the fish, led to the 

 conclusion that from two to three years after entering the ocean, many 

 of the males and a few of the females make their first journey up the 

 river to spawn. This accomplished, the fish return to salt water for 

 another period of about three years. Then occurs a second migration 

 to fresh water by a large proportion of both sexes. The males of this 

 migration average seventy centimeters in length, the females seventy- 

 six centimeters. Probably all of the salmon that have survived the 

 dangers of marine life unite in the third migration. The average 

 males of this age have attained a length of eighty-two centimeters, the 

 females ninety centimeters. These differences in size Miescher re- 

 garded as the result of another period of life and growth in the ocean, 

 between the second and third migrations, of at least two years. As 

 only a few salmon of ninety-eight to a hundred centimeters length are 

 taken, and these are all males, it is probable that the females as a rule 

 make only two journeys to the spawning grounds during their lives, 

 while the males ascend the river three or even four times. Within con- 

 siderable limits of error the probable age of the largest salmon taken in 

 the Rhine is therefore fourteen years. 



By a careful comparison of the statistics of the number of the 

 salmon taken in Holland and at Basel, Miescher found that any marked 

 increase in the catch in the lower reaches of the river was regularly 

 followed, after an interval of eight or nine weeks, by the appearance 

 of an unusually large number of the fish in Switzerland. Basel is five 

 hundred miles from the mouth of the Ehine, and if the average current 



