364 Part III. — Twentieth Annual Report 



lb will be noticed that in some cases the averages at diflferent dates 

 do not correspond as one would expect. This appears to have been 

 due sometimes to scanty numbers, or difierence in depth or habitat, but 

 in most cases it wa« due to insufficient i-epresentation of the series. In 

 most cases the small-meshed net employed had meshes of about 1 cm. from 

 knot to knot (fig. La, p. 326), and very small dabs, which are not only 

 narrow, but soft and pliable, no doubt escaped in considerable numbers. 

 The smallest specimens caught in this net measured usually forty or 

 over forty mm., sometimes a little less, whereas the completely trans- 

 formed dab is estimated above to measure from 16 to 18 mm. Some of 

 the hauls were made with a net having finer meshes measuring 6 mm. 

 from knot to knot (fig. Lb), and in these cases the proportion of small 

 dabs was greater, the smallest measuring 25, 26, 28, 30, 32 mm. The 

 hauls made with this net were on 15th January 1901, in Aberdeen Bay, 

 and those in the Firth of Forth, while those collected in the Moray 

 Firth in December and January, and those caught in the Solway, were 

 taken with a shrimp-trawl. 



It is evident, therefore, that the ranges and averages in the Table do 

 not in the great majority of cases represent the real ranges and averages, 

 owing to the fact that a considerable proportion of the smaller fishes 

 belonging to the series were not caught. The average size is too large 

 and the range too small. It is thus necessary to consider the evidence 

 in detail. 



The series clearly comprises the brood of the year, which originated 

 in the preceding spawning season. The first of my collections in which 

 they occur is that made on 23rd July in the Firth of Forth, when 103 

 were taken, ranging from 32 mm. (1| inches) to 49 mm. {\\^ inches), 

 the average size being 40 7 mm., or 1^ inches. They were taken with 

 the fine net. They formed a compact group, giving a columnar curve, 

 and the largest was separated from the smallest of the older series by 

 an interval of 19 mm. The largest at 49 mm. shows the apparent 

 maximum growth from the beginning of the spawning season at the 

 end of February, or early part of March, but the smallest at 32 mm. 

 does not represent the inferior limit, since we know that they may be 

 got on the bottom at 20 mm. and under. If we place this limit at 

 18 mm., then the range at this period becomes 31 mm., and the median 

 ordinate or average size 33*5 mm., or 1^ inches, which would represent 

 the average amount of growth in length from about the early part of 

 May. By this reasoning the average, as computed directly from the 

 haul, is too large by 7*2 mm., which is equivalent to the error introduced 

 at this period by the imperfection of the net. 



Collateral evidence on this point is aSbrded by the growth of the next 

 older series in this haul from the previous hauls on 9th and 1 3th May, 

 the latter date approximately representing the maximum of spawning. 

 The second series in May, consisting of 84 specimens about one year 

 old, had an average size of 67'5 mm. (2| inches), the smallest being 

 42 and the largest 98 mm. On 23rd Jiily the range extended from 

 68 mm. to 127 mm., and the average size was 101mm. (4 inches), or 

 33'6 mm. greater than in May, the diflFerence representing the amount 

 of growth in the interval. This, it will be observed, is almost precisely 

 the same as the mean increase computed for the first series during the 

 same period, viz., 33'5 mm. It is just possible, however, that the 

 smallest fish taken, viz. 43 mm., does not represent the real minimum 

 size in May, although it is 10 mm. larger than the smallest taken with 

 the same net in July. The reason of the doubt is that the range from 

 the largest to the smallest is 56 mm., which is rather too low, and while 

 a larger collection would tend to increase the upper limit slightly, it 



