666 



to tlie relative reduction of the sizes of its images, a diminution of 

 tlie distance from the ol)jecls of his sphere of feeling and acting 

 and a diminution of the rapidity of movement in proportion to the 

 lengths of the bodies. 



The conclusions we have thus obtained gixe an explanation of a 

 number of otherwise incomprehensible deviations in the value of the 

 coefficient of cei)halisation. 



For Bats I calculated in 1897 a (mutual) exponent of correlation 

 of 0.66... It ai)pears that it can be applied both to Macro- and to 

 Microchiropteres. A very lai-ge insectivorous Bat from Dahomey 

 (Scotophilus gigas) supplies a welcome control and affirmation of 

 my former results. In Bats the influence of the eye is almost 

 entirely excluded. The senses of touch and hearing determine the 



quantity of brain and the factor S^-^' ■ or 7> disappears. Calculated 

 with their own exponent of correlation the coefficient of cephalisation 

 still diminishes for the two phylogcnetically different groups, of which 

 the Microchiropteres are lowest. 



Rodents deviate mutually considerably in the values of their 

 cephalisation. This cannot be explained, as Lapicque surmises, by 

 different size of the eye, though it may play in some cases an in- 

 ferior part. It is the other senses especially, which, by taking the lead 

 in the nervous life of the animal, determine here the cpiantity of 

 brain. According to numerous evidences the cephalisation of the 

 Brown Rat and the Black Rat and likewise that of the Housemouse 

 is half that of Hares (and Rabbits) and only a third part of that of 

 Squirrels. In the Hares the sense of hearing, in the Squirrels, the 

 Desert Jerboa (Dipus) and the Garden Dormouse (Eliomys) especially the 

 organ of touch, on account of its high specification (in the hand), has 

 caused the increase of the brain. 



The value of k falling very low in Shrews, is trebled with the 

 aflined East-Indian Tupaja, which lives like the Squirrel. 



Canides have about twice as high a cephalisation as Mustelides, 

 on account of the greater development of their senses of hearing 

 and of smell. Among the last-mentioned family. Otters are hand- 

 animals, and, for that reason, they surpass very considerably the 

 other Mustelides in their cephalisation. They reach the rank of Canides. 



The Elephant surpasses the other Hoofed Mammals three times in ce- 

 phalisation. He ranks even much higher than the Anthropoid Apes. He 

 owes this to his trunk, which has become a prehensile and touch 

 hand, with high "specilic energies", and possesses the same combina- 

 tion with a chemical organ (here of smell) as the feelers of Ants. 



