TARSIUS SPECTRUM i in- 



gest extensive equilibratory needs; but the long, swift leaps which it makes, 

 not unlike volplaning, would almost certainly require a capable mechanism 

 for maintaining balance. Compared with other primates, tarsius may be 

 considered c[uite alone in the specialization of this peculiar llight-like type 

 of locomotion. In the case of lemur and marmoset, the leaping propensities 

 have a different character, appearing to be intermediate steps in a continuous 

 process of passing from one point of support to another. In this act, all four 

 extremities and the tail participate. The gibbon is another example of 

 flight-like passage through the trees, but in the case of this latter primate, 

 the arms are the principal means of locomotion in the long swings from 

 branch to branch. Tarsius, on the other hand, executes its leaps more in 

 the nature of long dives or upward hops in which it glides through the air for 

 considerable distances in order to reach its next objective. If it is true that in 

 these dives it captures insects on the wing, then the delicate balancing needed 

 for its locomotion is all the more apparent. 



The great prominence of the vestibular area must depend upon some 

 such specialization as this in tarsius, although it is to be regretted that no 

 authentic statements are forthcoming concerning the actual equilibratory 

 development of this animal. It is remarkable and noteworthy, however, 

 that tarsius leads all the primates, and for that matter most of the mammals, 

 in the high specialization of its vestibular nuclei. 



At this level the fourth ventricle is widely open and the lateral recesses 

 communicate with it over its dorsolateral angle. The uvula lills the entire 

 ventricular cavity. On the lateral margin of Deiters' nucleus (ND) are 

 the collected bundles of the inferior cerebellar peduncle (ICP), while 

 ventral to the nucleus is the substantia gelatinosa of Rolando (NR). 

 Along the outer border of the latter structure lies the descending trigeminal 

 tract (Trd). The rubrospinal ( Rst) and spinothalamic tracts ( Spt) occupy a 

 position upon the outer edge of the formatio reticularis ( Ref ). The posterior 



