RETROSPECT AND CONCLUSIONS 101 



finding of a moving j)rey, and are stimulated by the impressions 

 received from the hxteral-line organs. 



We must now refer to the valvuhv cerebelli. We are not quite 

 in the dark even about the functions of tliis difficult area. There 

 is no doubt that those fish like the barbel, the gudgeon and the 

 loaches which grub among stones and gravel for their food have the 

 tecta optica widely separated by the prominence of the valvula 

 and a freak development of a very highly elaborated valvula occurs 

 in a group of fishes with strongly curved snouts, the Mormyridae : 

 this suggests that tliis part of the cerebellum may be associated 

 Mith the grubbing habit, correlating the tactile, olfactory, and 

 gustatory sensations. In this connection it is well to recall that 

 fibres from the lobi inferiores and also gustatory fibres enter an 

 area at the base of the valvula. 



Herrick is our authority for some evidence as to the termination 

 of the ascending secondarj^ gustatory tract of both facial and vagal 

 lobes ^^•hicll is stated to be in a nucleus, situated in the lateral wall 

 of the isthmus. The chief gustatory tract arises from it and some 

 of these fibres pass to the lobi inferiores. He also gives a diagram, 

 in which an olfactory conduction path terminates in the lobus 

 inferior. It would indeed be surprising if we could fit in everything 

 in this nem"ological puzzle ; but an attempt has been made by the 

 comparative method to supplement the knowledge that has been 

 gained by other methods ; there can be little doubt that more 

 observations ^^'ill be made and some conclusions confirmed, and 

 others revised or extended. 



To sum up the new views that have been suggested by the 

 methods of comparative anatomy : the cerebellum is the centre 

 whereby the position of the animal in space is recognised and the 

 semi-circular canals are in close cormection with its main body ; the 

 central, acoustic area is the auditory centre and most of the fibres of 

 the eighth nerve enter it ; the lateral-acoustic areas are associated 

 with direction, and direction in a vertical plane is well shown by 

 a study of their enlargement in abysmal fishes ; the valvula is 

 associated with habits of grubbing, and the taste and olfactory 

 functions, and may also be a correlation centre of these functions. 



The posterior crura of the cerebellum or the continuation of 

 the acoustic-lateralis area into the medulla oblongata leads into 

 those parts of the medulla bounding the anterior portion of the fourth 

 ventricle ; this area is the skin area and is often enlarged and globular, 

 forming the somatic-sensory lobes or fifth lobes ; these lobes are 

 usually much developed in predatory fishes. This is well shown 

 in a study of the gadoid brain in which we find such fish as the 



