28 THE LOWER PRIMATES 



nicety in balancing and the greatest precision in all movements. 



Measurements and Indices of Lemur Mongoz 



The measurements of Lemur mongoz are: 



Total length 876 to 906 mm. 



Skull in its occipito-nasal diameter 76 to 82 mm. 



Skull in its bitemporal diameter 27 to 31 mm. 



Width of the brain case 35 mm. 



The dimensions of the brain, including the cerebellum and brain stem, 

 are 45 mm. longitudinally and 32.5 mm. transversely. 



Total weight of the brain 18 gms. 



Total water displacement 17 c.c. 



Weight of the forebrain 14.5 gms. 



(including endbrain and interbrain) 



Weight of the midbrain i gm. 



Weight of the hindbrain 2.5 gms. 



Upon the basis of these figures the following encephalic indices have 

 been computed for the several divisions of the brain: 



Forebrain index 81 per cent 



Midbrain index 5 per cent 



Hindbrain index 14 per cent 



A forebrain index of 81 per cent definitely aligns this animal with those 

 forms in which the inception of manual development is already under way. 

 The highest forebrain index of what may be called the submanual group, 

 such as the dog, cat and horse, is 80 per cent. The lemur marks the transi- 

 tion line between the manual and submanual groups. 



