6oo ffm. E. Kellicott 



tive character of a sample. The determination of the "probable 

 error" of a datum can not take into account any error of observa- 

 tion. 



2 Variability 

 a Comparative Variability of the Sexes 



The relative variability of man and woman is a much discussed 

 subject and exact data are fairly abundant but among other forms 

 exact data are by no means abundant. In man while neither sex 

 is uniformly the more variable it seems now that, quite contrary to 

 the former belief, the female is usually more variable than the male. 

 Pearl ('05) gives a summary of the coefficients of variability in 

 man compiled from various sources. Of 41 characters of many 

 kinds the female is more variable in 25, the male in 16, the differ- 

 ence rarely exceeding 15 per cent of the male value. Pearson 

 ('97) also showed that on the whole the ratio between the averages 

 of a large number of coefficients of variability in various races in 

 man and woman is .973, showing that is, a slightly greater vari- 

 ability in woman. Among other mammals Davenport and BuUard 

 ('96) show the variability in the number of Miillerian glands in 

 swine to be 2^ per cent greater in the male than in the female. 

 Minot's ('91) data on the weight at birth of male and female 

 guinea pigs (Cavia) give coefficients of 23.94 and 22.62, respect- 

 ively. Montgomery ('96) states that in a number of species of 

 birds the males are more variable than the females in about 60 

 per cent of the measurements made; his results can not be stated 

 in terms of the coefficient of variability. In the shrike (Lanius) 

 Strong ('01) measured four external characters and found very 

 slight differences between the sexes, the male perhaps being 

 slightly the more variable. 



In Necturus Bumpus ('97) found the males less variable than 

 the females with respect to abnormally placed pelves, but again 

 the results can not be expressed as coefficients. In the toad (Bufo) 

 we have found not only that the females are more variable than 

 the males in every one of the twelve characters compared but that 

 they are very decidedly so — from 6.6 per cent to 38.4 per cent, so 



