of the Fishery Board for Scotland. 353 



it would still exist. The measui'ements of the fish in the hollow, from 

 120 to 190 mm., have been plotted out in 5-mm. and 2-mm. groups, with 

 and without the multiplication by seven of the first series, and the fact 

 is brought out that the plaice between 137 and 175 mm. are imperfectly 

 represented in the hauls, and are no doubt those which were on the 

 bottom between seven and nine fathoms, an interval in which the trawl- 

 net was but little used in either haul. 



The first question to decide is whether these fish, so scantily present, 

 belong to an intermediate series, or to the larger or smaller series, or 

 partly to one and partly to the other. The evidence is against the view 

 that there is a missing series, because the space is too small for its 

 intercalation, and if a curve to represent an imaginary group is inserted, 

 the overlapping would be far greater than between the succeeding older 

 series, where overlapping is always greatest. Moreover, we have seen 

 that the small plaice of the Solway grow about 60 mm. in their first 

 year, and if a group were inserted, and only the same minimum rate of 

 growth assumed for the succeeding series as for the first, wo should have 

 the averages for the groups as 60, 120, 180, and 240 mm., which, as the 

 curve shows, cannot be true. 



The plaice of intermediate size appear to belong to both series, but 

 far more to the second than to the third. Some do, however, appear 

 to belong to the third series, as the slopes of the curve suggest^ but their 

 pi'esence would not tend to distvirb the maximum ordinate and arith- 

 metical average of that series to any great extent— not more, probably, 

 than a few millimetres. A study of the evidence makes it almost 

 certain that the missing fish belong mostly to Series II., because, as this 

 series stands, it shows an increase of only 58 mm. for the second year's 

 growth, whereas it is certain the second year's increase in length is 

 greater. If the fish were present in due proportion the maximum 

 ordinate and arithmetical average would be shifted nearer to Series 

 III., and from a study of the curves in this and other cases it is pro- 

 bable they should lie about 13 or 13'5 centimetres, and the apparent 

 yearly increment of growth would be correspondingly increased to about 

 70 or 75 mm. from the first series to the second, and reduced from the 

 second to the third to 80 or 85 mm. 



There is probably a first series, about six or seven months old, ranging 

 in size from under 40 to 85 or 90 mm., and with a mean size of about 

 65 mm. (or 2^ inches); a second series ranging from about 90 mm. to 

 160 or 165 mm., and with a mean size of about 137 mm. (5| to 5| 

 inches), and the third series, referred to below, with a mean size of about 

 215 mm., or 85 inches.* 



The later groups of older fishes are also imperfect, as may be seen from 

 the position of the peaks, or maximum ordinates, in the figure and this 

 also is mainly due to the depth of water in which the hauls were made, 

 the larger fishes being further out from shore. 



*A haul with the shrimp-uct in Alierdeoii Bay. in from 4 to 10 fathoms, on 9th May 

 1902, furnished 126 iilaico, of whicli the first series comprised 98, ranging from hi to 

 126 mm., the arithmetical average hciug 92-2 mm. (3| inches), and the median ordinate 

 on Lasu-line 92-5. These fish wore nearly 14 months old. The second series was 

 imperfect ; it comprised 28 from 140 to 227 mm., the arithmetical average being 190-8, 

 and the median ordinate 185 nmi. (~\ inc^hes). 



I Tablk 



