52 

 the facts. The systeni is, prin.arily, a tactile apparatus for 

 the heaj. Any one who has watched Wustelus exploring with his 

 snout every corner of a new aquariuir cannot doutt that tactile 

 impressions from this region must have a large place in the 

 life of the animal. With practically no other check upon his 

 visual sensations than can be derived from poking his nose 

 into things, widely spread central terminations of cutaneous 

 fibres is no more than should be expected. 



7. 7 he TubefouluTT. Acusticum. 



The tuberculuir acusticum is the trigeminal lobe of Viault 

 ('7'^:), Hohon ('77), ynd Sanders CS^); Kingsbury ('97) has 

 extended the teriii oerebel lar crest to the entire structure; 

 while Johnston ('98b) appears to include under his tubercului 

 aouaticuT. all those structures in the oblongata which are homol- 

 ogous with the dorsal cornu of the spinal cord. The term tri- 

 geminal lobe has been so variously used that it should be drop- 

 ped from our nomenclature. The earlier writers on the brain 

 of the selachi3.n so designated the tuberculuir acusticum, sup- 

 posing, erroneously so, that the great trigeminal complex, 

 which emerges just beneath its anterior end, must have the 

 origin of its nerve-roots here. 



The tuberculum acusticum is the prinary terminal station 

 for the acustico-lateral system. Fibres from the lateral line 

 sense-organs and the internal ear are components of the VIl, 



