650 



calculation for each tiirie two Mammals of differeiit orders: Primafes, 

 Ruminants, (Carnivores, Rodents, always only values varyin»; mntuallv 



5 

 between 0.54 and 0.58, with an averaoe of 0.56 or about - = 0.55 . . . 



9 



Arranging accordijig to k calculated in this way, we see indeed 

 the great confusion prevailing in the arrangement of Mammals accord- 

 ing to the relative weights of their brains, give place, in a generally 

 satisfactory manner, to an arrangement that is pretty well in con- 

 formity with the natural system. A few deviations coutinue to exist, 

 the Elephant e. g. takes his place between Man and the Anthropoid 

 Apes, f he Rodents deviate mutually very strongly. On the other 

 hand the different behaviour of Macrochiropteres and Microchiropteres 

 indicates rightly theii' different origin. 



In 19(J5 the above-mentioned method of investigation was applied 

 to Birds by Louis Lapicque and Pierre Girahd ^). Ky 5 comparisons 

 (Hooded Crow — Jay, Carrion Crow — Jay, Wild Duck — Summer Teal, 

 Silvery Gull — Sea Swallow, Buzzard — Kestrel) they obtained for r 

 a value that was so near the one I found for Mammals, that 

 their conclusion, that for Birds the same exponent of correlation 

 may be accepted, was entirely justified. According to the value of 

 the coefiicient of cephalisation calculated by this method, Birds, 

 though not entii'ely after the natural system, yet with regard to the 

 nearest affined ones, may be classified in a natural way. Parrots, the 

 Monkeys among Birds, stand highest in the list '^). 



Afterwards a few other comparisons (Swan — Summer Teal, Eagle- 

 Kestrel, Parrot— Parrakeet, which species showed greater differences 

 in the sizes of their bodies), could be added by Lapicque ^) to the 

 first 5 comparisons ; in this way still better results were obtained. 



The 5 most thrustworthy comparisons gave now an average r=0. 558. 



This constant returning of "cette puissance étrange" 0.56, the 

 meaning of which is absolutely incomprehensible according to 

 Lapicque "), likewise in Birds, where the anatomical composition 

 of the brain is certainly very different from that of Mammals, must 

 indeed be called exceedingly striking. 



Under these circumstances it was of great interest to investigate 



^) Gomptes rendus des seances de TAcademie des Sciences. Paris J 905, 1 , Tome 

 140, p. 1057—1059. 



2) Bulletins du Muséum d'histoire naturelle. Paris 1909. p. 40S— 412. 



8j Revue du Mols, Paris. 10 Avril 1908. 



^) Revue du Mois. Avril 1908. p. 445. Furtlier : Bulletins et Mémoires de la 

 Société d' Anthropologie de Paris. Seance du 2 Mai 1907. 5me Série, Tome 8, 

 fasc. 3. Paris 1907, p. 261. 



