392 



DR MATTHEW YOUNG. 



There are other causes that operate against uniformity in the curve of frequency ; 

 and one that is specially noticeable in the curves given at the end of this paper for 

 the indices is the small size of the unit compared with the number of skulls in the 

 series. The indices have been calculated to '5 as well as to whole numbers, which 

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Fig. 6. — Frequency curve for height index in 100 male and 100 female skulls. 



curves, many of the indentations would not have been present had one point been the 

 difference between one index group and the succeeding one. According to Fawcett, 

 ; ' it would be quite unjustifiable to argue from a series of peaks as to racial mixtures. 

 Even if like peaks occur in the two sexes for several characters, the sources of hetero- 

 geneity given above are often ample explanation." 



(C) The Correlation of the Characters of the Scottish Skull. 



Correlated variability is such a relation between the magnitudes of two or more 

 characters that any abmodality of the one is accompanied by a corresponding 

 abmodality of the other or others. The length of this series and the remarkable 

 uniformity of the type of skull represented presents an almost unique opportunity 

 for the study of the correlations of cranial characters. 



As the possible combinations of the various measurements I have made of the 

 different skulls, taking two at a time, would amount to a very large number, in fact 

 some thousands, it is necessary to make a selection of the characters for the purposes 

 of correlation. My choice has been regulated largely by those for which I can find 

 comparative figures in other races, and so resembles closely, in so far as it goes, the 

 list given by Fawcett and Macdonnell, which includes those characters of special 



