238 



adult individuals of four species of the genus Caiiis. In Fig-. 2 tliey 

 are again exponential curves, defined, for tlie Doniestic Dog, by the 

 equation 7^; = ƒ/'"-"» = 8.475 I*^'^* {in which ƒ is found from 



89 = / X 18000), and (or the \vild (;aiii(iae, /i;= 4.615 P./iii which 



52 \ 

 4.615 = — ;- — — 1. In Fig. 3 they are straight lines, l)0th of them 



less steep than the lines for these relations from S|>ecies to species, 

 which they intersect in (he points of the means, as far as the wild 

 species are concerned. I have derived the mean poin-t for the Domestic 

 Dog, and the line for theindividual relati(>n within this species from 

 observations of weight on 434 dogs, i. e. 152 new ones by Klatt '), 

 Rtchet's 188 observations *), Lapicque and Dhérê's 47 *), Rüdinokh's 

 19*), Wii,dkr's 16'), iMax Webku's 12'). On the ground of these 

 data 18 kg. maj- be admitted for the mean weight of the Domestic 

 Dog, 89 gr. for its mean brain weight. The brain weight is certainly 

 at least 6 7o. pi'obably 10 7o lower than in a Avild species of Canis 

 of the same weight. This can only be considered as a consequence 

 of domestication, i. e. of unnatural mode of living. Something ot 

 the same kind was found by Donaldson and Hatai ') in the domesti- 

 cated albino-form of the Brown Rat (Miis norvegicus). Not only 

 the body weight has been reduced in this domestic Rat, but the 

 brain weight comparatively to a greater degree, a phenomenon of 

 domestication due to a diminished growth of the brain, which was 

 already known to Darwin (1868) for the domestic Rabbit **), and 

 which was afterwards confirmed by Lapicque "), Klatt ^*), and 



^) B. Klatt, I.e. Haupttabelle at the end of his work. 



') Ch. Richet, I.e. 



') L. Lapicque in Bulletins et mémoiies de la Société d'Anthropologie de Paris 

 1907, p. 316. 



•*) N. RüDiNGER, Ueber die Hirne verschiedener Hunderassen. Verhandliingen der 

 Anatomischen GesellschafL Jena 1894. Erganzungsheft zum 9. Band (1894) des 

 Anatomischen Anzeigers, p. 173 — 176. 



*j B. G. Wilder, Cerebral Variation in Domestic Dogs. Proceedings of the 

 American Association for the Advancement of Science, 22"'' Meeting (1873), p. 235 — 

 236. Salem 1874. 



*) Max Weber, Vorstudien fiber das Hirngewicht der Saugethiere I.e., p 112. 



7) H. H. Donaldson and Shinkishi Hatai, A Comparison of the Norway Rat 

 with the Albino Rat. Journal of Comparative Neurology. Vol. 21 (1911), p. 417- 

 458, particularly p. 454 — 455. 



8) Gh. Darwin, The Variation of Animals and Plants under Domestication. Chap. IV. 

 8) L. Lapicque in Bulletins et mémoires de la Société d'Anthropologie de Paris 



1907, p. 331—337: , Regression cerebrale des animaux domestiques". 



1*^) B. Klatt, Ueber die Veranderung der Schadelkapazilat in der Domestikation. 

 Sitzungsbericbte der Gesellschaft Naturforschender Freunde zu Berlin. 1912, p. 155 



