of the Fisher II Board for Scotlanrl. 375 



indicated an apparent growth from October of 2S'3 mm. Tiie number 

 of specimens is too small to make these conclusions reliable. 



Another haul was made on 1 1 th December 1901 , 75 miles S.E. of Sum- 

 burgh Head, in 75 fathoms of water, and 1830 long rough dabs were 

 obtained. The first group comprised 28 individuals, ranging in length 

 from 45 to 61 mm., and having an average size of 54*4 mm., or 2^ inches. 

 These fish were about ninfe months old. The next series, the measure- 

 ments of which give a very complete curve, comprised 1249 specimens, 

 614 females and 635 males (PI. XVII.). The females varied in length 

 from 79 mm. to 134 mm., with a I'ange, therefore, of 55 mm., and an 

 average size of 104"8 mm., or i^ inches. The males extended from 81 

 mm. to 118 mm., with a range of 37 mm. and an average size of 98*4 

 mm., or 3| inches. 



When we contrast these measurements with those of the corres- 

 ponding series in May (which was then the first series, the sexes of 

 which were not determined) the mean increase amounts to 33 mm., or 

 1-j^ inches. This represents the apparent growth during the 216 

 days throughout the summer and autumn for the group with the males 

 and females combined. 



If we compai'e the measurements of December 1901 with those of 

 October 1900 it will be seen that while the average size of the first 

 undifferentiated group is greater by 1*1 nun. in December than in 

 October, the averages for the males and females of the second series for 

 the combined undiflferentiated group are somewhat less. Thus, while 

 in October 1900 the females had an average length of lll'4mm., in 

 December 1901 their average length was 104"8 mm., or 6"6 mm. less. 

 The males at the former period had an average length of 102*5 mm., 

 while at the latter period their average length was 98*4 mm., or 4*1 mm. 

 less. The range of sizes in the two cases is almost alike — viz., for the 

 females from 79 to 136 mm. in October, and from 79 to 134 in 

 December (the next largest being 1 38 mm.), and for the males 81 to 

 123 mm. in October, and 81 to 118 mm. in December. In the latter 

 Ciise (males) the range in December is 5 mm. less ; but there are only 

 thi'ee between 118 and 123 mm., the transference of which from one 

 group to another would make no appreciable difference in the average. 

 The curves in both cases are good, the numbers are large, and tlie 

 2-millimetre grouping shows that the point of division between the 

 groups is as indicated. 



The conclusion, therefore, appears to be that the environmental 

 conditions for the growth of the long rough dab were more favourable 

 in the summer or autumn of 1900 than in 1901. Probably the bottom 

 temperature was lower in the latter yeai". 



The limits of the larger series in the December hauls are not very 

 clearly defined. The females of the third group begin with a size of 

 138 mm., and an examination of the 2-mm, grouping shows that the 

 series may end at 173 or at 183 mm. The former is the best, because it 

 corresponds with the rest of the cm-ve (see PI. XVII.), and the group as 

 thus defined comprises 207 females, having an average size of 155-7 mm., 

 or 6^^ inches, and this is O'l mm. more than the corresponding average 

 in October, The group of males extends from 121 to either 149 or 

 157 mm.; if the latter is selected, the average size of the group is 

 138'7 mm., or 1-1 mm. greater than in October. 



The fourth group is still less easily defined. The'_ females, numbering 

 140, appear to extend from 174 to 219 mm., with an average size of 

 198-6 mm., or 7|| inches; and the males, 21 in number, from 158 to 

 178 mm., with an average of 166-0 mm., or 6^^ inches. There appears 

 to be a fifth group of 21 females from 221 to 257 mm., and having an 



