BRAIN PATTERN 25 



furnished witli taste-buds, with which it searches for shrimps, 

 small molluscs, Morms, and insect larva?, in the sand and gravel. It 

 has rather a curved snout and thick lips so that it is a typical " skin- 

 taster." and therefore we find a very large facial lobe. But this is 

 not the whole story of the facial nerve and lobe in the gudgeon. If 

 the facial nerve is traced into the lobe it will be found to divide into 

 two j)arts. an anterior bundle of fibres passes laterally into the front 

 of the facial lobe, and a posterior bundle passes backwards into the 

 hinder part of the lobe, thus dividing the lobe into two separate 

 areas. There are other fish which have a similar cU vision of the 

 facial nerve within the brain ; for example the barbel, which has 

 two pairs of barbels ; in this fish the bmidles are of unequal size, 

 the anterior is small, ^^■hile the posterior is larger and enters a large 

 division, forming the hinder part of the lobe. 



The tench is also the possessor of a similar division of the facial 

 nerve, but it has only a short barbel on either side of the mouth ; 

 associated with this small barbel we find that there is a large lateral 

 bundle passing to the front of the facial lobe and a very small strand 

 passing to the hinder portion. We see, therefore, that the size of 

 the two parts of the lobe varies with the development of the barbels, 

 in the barbel a large posterior portion with many barbels, and in the 

 tench a small posterior portion with a single small barbel on either 

 side. These conchtions have also been found to occur in certain 

 Cyprinoid fish of the Madras tanks as noted by Bhimachar, who 

 describes a fish very like a tench with small barbels and a small 

 cUvision of the nerve passing posteriorly. The conclusion appears 

 to be justified that fish with barbels have a division of the facial 

 lobe, and that it is the posterior part of the lobe that receives the 

 gustatory fibres arising from the taste-buds of the barbels, at any 

 rate in the Cyprinoid family. 



This observation concerning the differentiation of two bundles 

 of the facial nerve reminds the writer of the remark of tSir Charles 

 Bell, " he who discovers a new nerve or furnishes a more accurate 

 description of the chstribution of those already known, affords us 

 information in those points that are more likely to lead to an accurate 

 knowledge of the nervous system." 



The brain of a roach is in sharp contrast with that of either 

 bream or gudgeon. Both vagal and facial lobes are small, but to 

 compensate the fish for this slight development of its gustatory 

 centres, it has large optic lobes, and is very sharp-eyed, so that very 

 fine gut must be used by the angler, if he wishes to be successful in 

 his sport. But it must not be considered that the roach is lacking 

 in the sense of taste, because every fisherman must have noticed 



