852 



namely the brain weight and the body weight are in a fixed, 

 causative ratio to each other. Tliis is, however, not the case, as I 

 propose to demonstrate '). 



In order to trace the canse of' the agreement found between 

 the relation of Man and Woman and that of the homoneuric 

 species, and at tlie same lime of the departure from the inter- 

 individual relation, it is required in the first place to examine 

 whether this agreement and this deviation is ijenernl, and furtlier 

 lioio the sexnal difference of the size of the body can have influence 

 on the quantity of brain. 



With regard to the first point Lapicquk examined, already in 1907, 

 whether for the common Rat (Mus norvegicns Erxl.) and the common 

 Sparrow (Passer domesticus L.) the male sex possesses an excess of 

 body weight and at llie same lime an excess of brain weight above 

 the female sex, as in the lunnan species'). He found this for both 

 animal species, least cleai-ly for the Rat. Of 15 full-grown male 

 sparrows and 13 full-grown fenuile spari-ows the average body weights 

 were 30.8 and 28.7 grams, and the average brain weights 994 and 

 959 milligrams, from which an exponent of relation of 0.5077 can 

 be calculated"). Given however the slight differences of the average 

 weights, which IjAPICquk himself (j). 747) calls oidy "approximatives", 

 added to the comparatively great individual deviations, not much 

 value should be assigned to this result. The body weight ranged 

 for the male spairows from 28.61 to 33 grams, for the female 

 from 26.30 to 31.10 grams; the brain weight for the nuJe sparrows 

 ranged from 825 to 1080 milligrams, and for the female sparrows 

 from 900 to 1110 milligrams! It is certainly not possible to con- 

 clude from this to a relation of the brain weight and the body 

 weight between the two sexes of a similar nature as for Man ; nor 

 did Lapicque feel justified in doing so. For the rest it is well-known 

 that the sexual difference in size for the Sparrow, if it does exist, 

 is only met with to a veiy limited degree. 



Sexual parity certainly applies to the Colin (Colinus virginiannsL.), for 

 which gallinaceous kind of bird Hhdlicka determined body weights and 



1) I have to rectify here my former erroneous assumption (These Proceedings, 

 Vol. XVI, p. 659) that this relation would be the same in general for Vertebrates 

 as for Man. 



') Louis Lapicque. Difference sexuelle dans le poids de I'encephale chez les 

 animaux: Rat et Moineau. Gompies rendus de la Société de Biologie. Tome 63 

 (1907), Seance du 21 décembre, p 746—748. 



') From the average weights of P and E in tlie two sexes repeatedly given there. 

 On p. 748 the result of this calculation has been erroneously given as 0.57 there. 



