92 



ANATOMY OF VERTEBRATES. 



the timid and sharp-eared nocturnal Aye-aye, being associated 

 with large external ears and a well developed auditory organ. 1 



In Man the lateral lobes of the cerebellum acquire their largest 

 proportions, are called 4 hemispheres,' fig. 63, c, and reduce the 

 middle lobe, which is the most constant part in the vertebrate 



Under surface of Humaii Cerebellum, xxvii". 



series, to the semblance of a subordinate adjunct, called ' vermiforrn 

 process,' ib. P, in Anthropotorny. 



The characteristic form of the human cerebellum is manifested, 

 according to the developmental law (' Preface,' vol. i. p. xxi.) 

 before its surface becomes convoluted, and when the large 

 hemispheres are represented by smooth vesicles of neurine, fig. 

 47, c, c. It resembles the cerebellum of the bony fish and frog 

 in the smoothness of the surface, but has assumed in the foetus at 

 four months the recognisable specific form. The cerebellum is, 

 in fact, more unique and definitely human at the embryonic 

 period than when fully developed ; it then weighs, or averages, 

 5 oz. 4 dr. in the male, and 4 oz. 12 dr. in the female. 2 



AVhen the under surface is exposed by removing or reflecting 

 the macromyelon, as in fig. 63, the middle lobe, P, is seen at the 

 bottom of a valley (vallccula, Haller, v) dividing the hemispheres, 



1 en'. 



A i". and XLIX". p. 4 (1862). 



