416 De he OM OTH [DECEMBER 
The second example taken deals with the group of plaice from St. 
Andrews. In one respect they do not precisely conform to the condi- 
tions necessary for obtaining a “pure” group, in that both male and 
female are taken. The warrant for doing so is that at the size (12 
inches on average) no distinct differences between the two sexes with 
regard to these characters can be detected. These are compared with 
the plaice from Grimsby and Aberdeen. The comparison is not made 
with the total averages of these last two groups, but only with those 
of two portions which are similar in all respects to one another and 
similar with regard to size and sex to those from St. Andrews. 
It has been known‘ that the plaice of St. Andrews Bay are the 
young of the plaice which spawn somewhere near the Aberdeenshire 
coast, and it was therefore of interest to find out if this new method 
of research would support the testimony obtained by another. 











Averages Sd rE Averages Spe Sd Averages 
Characters. for == — for — for 
Aberdeen. a me St. Andrews. & me Grimsby. 
Intermaxilla (2) 26°80 |+-4 16 26°40 58 | +°76) 27°16 
Intermaxilla (a)| 21:17 |—-1l | -278 21°70 D9 | —-O1| 20°92 
Tail (7) . 29°56 |+°23 | °467 28°64 2°08 | +°74| 30°89 
Hye (6) . 35°72 |+°085} °381 36°07 157 | +°49| 35°83 
Mandible 46°70 |+°194]| °384 46:07 1:305| +°30| 45°60 
Head (d) 39°09 |+°155| °32 39°13 143 | +°02| 37-73 
Head (6) 48-72 }4+°01 | °38 49°57 2°03 | —°46| 47-20 
Head (/) 24°31 |+°08 | °37 23°76 2°06 | —-09} 25°28 
Body height 65:18 |+°16 | -40 64°37 2°04 | —-23] 63:00 
C. Vertebrae .| 30°03 |+°14 | °36 30°05 1:84 | -—-22}| 30:07 
A. Vertebrae .| 12°96 |+°13 | °33 12°95 167 | —°19| 12°94 
Fin-rays P(r).| 11°53 |+°12 | °30 11°52 1:54 | —-20| 11°30 
. P(Z).{| 10:93 |+-095) -28 11°13 142 | —-20| 10°91 
sf A .} 54:28 |+:086| -26 54°31 1°33 —-21| 53°98 
Ks D .| 72°67 |+:°065| 247 (2°91 1-250] —-22| 72°51 


St. Andrews varies by -247 from Aberdeen, and 1°250 from Grimsby. 
The characters of this table might have been specially arranged in 
order to show a uniform gradation of the differences which are tabulated 
under the headings 2 and =e But they were tabulated just as they 
presented themselves, and the fluctuations in these differences instead 
of being a flaw in the principle only show how necessary it is to take 
more than a few characters. The small number of characters here 
taken, and the seemingly very slight differences between the two 
original groups of Grimsby and Aberdeen, make a severe test of the 
theory, and thus the results are the more convincing. The values of 
the deviations between St. Andrews and the other groups gradually 
1 Dr. T. W. Fulton: Rep. Fish. Board for Scotland, No. XI., 1893, Part III. p. 176. 
