8 



44"7 per cent., migrated to the north and east, for an average distance of 55*8 

 miles, the mean direction of all the experiments being N. 34° E., or nearly parallel 

 with the coast ; the number which migrated to the north and west was 114, or 

 19 per cent., the average distance being 16'2 miles, and the mean direction, N. 52° 

 W. ; those which travelled south and east numbered 47, or 52 per cent., the 

 average distance being 27"9 miles, and the mean direction, S. 33° E. ; while 149, 

 or 24*8 per cent., went to the south and west, for a mean distance of 8*7 miles in 

 the mean direction S. 53° W. The mean directions to the north and west in the 

 various experiments ranged from N. 39° W., a line which touches the coast about 

 Arbroath, and N. 71° W., a httle north of Fife Ness, while the mean for all experi- 

 ments in this quadrant, if prolonged, would reach Buddon Ness, at the mouth 

 of the Tay. The mean directions to the south and west ranged from S. 37° W., 

 a line which would touch the coast about Fast Castle, west of St. Abb's Head, to 

 S. 61° W., at Dunbar, and the mean direction of all the experiments, S. 53° W. 

 reaches the coast some miles to the east of Dunbar. 



II. It is obvious that the above method, although helpful in showing the 

 direction of the predominant migration, is not strictly accurate. While the general 

 direction is ascertained, the mean direction obtained is not equivalent to the 

 true resultant for the quadrant, since a short distance in one direction is given 

 equal value to a long distance in another direction. 



It was desired to ascertain the true resultant of all the varied migrations in 

 each quadrant, i.e. the hne and distance which would represent the net result of 

 the divergent movements of the individual fish. Tins was done, according to 

 ordinary mathematical methods, by Miss F. M. Mulholland, and forms the second 

 method adopted. In this case, the adult and immature of each sex were treated 

 separately, and in those fish which went northwards and then westwards, into 

 the Moray Firth, or to the north or west coasts, the initial direction alone was 

 taken into account. The results are shown in the following ^nble : — 



Adult Males. 



