855 



value of the intersexual exponent of relation still lies much nearer 

 0.28 than 0.56. 



Though the number of the individuals compared may he small, 

 together these comparisons appear sufHicient to prove that there 

 exists another ratio of the brain weights to the body weights between 

 the two sexes, very different from that in the human species. 



For not a few, probably for by far the most species there does 

 7iot exist sexual dimorphism in this respect, even where it might 

 be expected from the external difference in the size, as for the Ox 

 and the Domestic Hen. For those species which do not show sexual 

 din)orphism in the size of their bodies this is still less to be expected 

 in the brain weight. Of 16 male squirrels (Sciurus vulgaris L.) I 

 found i\*e body weight on an average 331 grams, and of 15 female 

 squirrels killed in the same neighbourhood on an average 326 grams. 

 Thus much may already be inferred from the not yet numerous 

 determiïiations of the brain weight, that for this species the greatei' 

 exponent of relation between the sexes does certainly not hold. 



For the human species, on the contrary, the important internal 

 dimorphism of the brain weight, which finds its expression in the 

 exponent of relation of double the value for other species, corresponds to 

 the striking external sexual dimorphism of the body weight ; in ratio 

 to the body weight man has a disproportionally greater amount of 

 brain than woman. 



Of great consequence is the fact that a Javanese monkey species, 

 the Budeng, Seinnopithecus maurus F. Cuv. (incl. pyrrkus Horsf.), 

 entirely agrees witli the human species in this respect, as follows 

 from the body weights and brain weights, according to determinations 

 by KoHi.BRUGGK ') of a number of male and female animals killed 

 in the state of nature. I mentioned this conformity in a few words 

 already in 1913'). This sexual dimorphism in the quantity ofbiain, 

 of the same nature and to the same extent as for Man is 

 most likely a general characteristic of the Monkeys, at least for 

 those of the Old World, for they show universally considerable 

 sexual differences in size of the body and at the same time a certain 

 sexual difference in the requirements of the mode of life, which in 

 Man are attended with the dimorphism of the quantity of the brain. 



Fiom the values of P and E determined by Kohlbkuggk for the 

 species mentioned, those which may serve for the calculation of an 



1) J. H. F. KoHLBRUGGE. Mlttheilungeii iiber die Lange und Schwere einiger 

 Organe bei Primaten. Zeits( hrift fur Morphologie und Anthropologie, Bd. II. 

 Stuttgart 1900, p. 54. 



«) These Proceedings, Vol. XVI, p. 659. 



