416 



H. M. KYLE 



[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 l 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. 



Characters. 



Intermaxilla (I) 

 Intermaxilla («) 



Tail (I) . 



Eye (b) . 

 Mandible 



Head (d) 



Head (b) 



Head (I) 

 Body height 



C. Vertebrae 



A. Vertebrae 



Fin-rays P(r) 



,, P(0 



„ A 

 D 



Averages 



for 



St. Andrews. 



26-40 

 21-70 

 28-64 

 36-07 

 46-07 

 39-13 

 49-57 

 23-76 

 64-37 

 30-05 

 12-95 

 11-52 

 11-13 

 54-31 

 72-91 



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 — and — . 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. XL, 1893, Part III. p. 176. 



