of the Fisher n Board for Scolland. 309 



one haul by twenty-one females from 136 to 218 mm., with an average 

 size of 1730 mm., and seven males from 135 to 193 mm., and an average 

 size of 162 mm. The curve is very irregular and imperfect and the 

 numbers small. A better curve is given by the second liaul on the same 

 day, in which 308 dabs whose sexes were not determined, ranging from 

 131 to 219 mm., had an avei-age size of 167*3 mm., or 6y^^ inches. In this 

 case the curve is quite symmetrical to 19 cm., and then is irregular, and 

 the maximum ordinate is at 16 cm. On 5th July the series was well 

 represented by seventy-nine females from 1 48 to 224 mm , and an average 

 size of 178"7 mm., or 7 inches, and forty-one males from 143 to 222 mm., 

 with an av-erage of 176'9 mm., or 6]-^ inches; the mean size of the group 

 with sexes combined being 178"1 mm., or 7 inches. On 31st July the 

 mean size of 109 females was 195"7 mm. (7|^ inches), and the range from 

 163 to 239 mm.; the mean size of 31 males was 185*3 mm. (7^^ inches), 

 and the range from 164 to 224 mm., the mean size of the mixed group 

 being 193'0 mm., or 7i inches. 



In the Firth of Forth on 9th- 13 th May, twenty -six females ranging 

 from 109 to 178 mm. had an average size of 148'0 mm,, or 5|| inches, 

 and 21 males, an average size of 151 "4 mm. (5y|^ inches) and a range 

 from 111 to 181 mm., the mean size of the group being 149"5 mm., or 

 5j7 inches. On 23rd July the mean size of the mixed gi-oup, now the 

 third, was 179"1 mm., or 7iL inches. 



It appears from these averages that the mean size of the common dab 

 in the Firth of Foith when about two years old is nearly 150 

 mm., or about 5^ inches in length ; it is probably less in Aberdeen Bay. 



The next older series is not very fully represented in most of the 

 hauls. In Abei'deen Bay in September 1900, 278 females had a range 

 from 176 mm. to 267 mm., with a mean size of 213"4 mm., or 8y^^ inches, 

 and 52 males, ranging from 175 to 246 mm., had a mean size of 

 205"9 mm., or 8i inches. On 13th October the mean size of the females 

 was 21 6*4 mm. (8| inches), and of the males 199 mm. (7Yf inches). 

 In December the mean size of 49 females was 2503 mm., or 9^ inches, 

 and of four males 241 "8 mm., or 9| inches. The differences are due 

 principally to unequal representation of the groups. 



Comparison may now be made of the apparent annual increment of 

 growth from one series to another, and m the following Table are given 

 the differences between the averages as deduced from the actual 

 measurements of the different series. 



I Table. 



