CHAPTER III 

 THE CARPS 



It is fortunate that the most suitable fish for the study of form and 

 function, and the relation of bodily structure to brain pattern, are 

 among the commonest fish in the rivers, lakes, and broads of our 

 native land. We refer to the carps or Cyprinoids, and for our 

 purpose we have examined the brains, both by the naked eye and 

 by microscopical methods, of the following fishes, the carp, goldfish, 

 bream, tench, roach, rudd, dace, minnow, chub, bleak, barbel, 

 gudgeon, and the loach ; the last, though not strictly a Cyprinoid, is 

 so nearly related, and so similar in many ways to the gudgeon, 

 that it is included in the list. British Cyprinoids subsist on a mixed 

 diet, some are almost entirely vegetarian, some feed on insects, 

 shrimps, worms, flies, and larvae and some on small shellfish. A 

 few are at times predacious, as the chub, and others, found mostly 

 in large lakes, are almost entirely surface feeders and might almost 

 be called plankton-feeders. 



It will be found that these fish can be arranged into groups 

 according to their diet and habits, and that each group has a charac- 

 teristic brain-pattern ; and further it is found that these groups 

 correspond to the groups given by Tate Regan in his synopsis, based 

 on external characters only, of the British species of Cyprinoids. 

 It is necessary to supplement the naked eye description of the brains 

 of these fish by microscopic methods, but in the first place we will 

 be content to describe the naked-eye appearances ; but it may now 

 be mentioned that a lack of the study of serial sections has led to 

 many erroneous statements in the past. A study of the Plate 3 

 will enable the reader to see at a glance the striking difference in 

 the brain-pattern of the three groups ; but a short descriptive 

 account will serve to emphasise the more important details. 



Group I. — Carp, Goldfish, Bream, and Tench. 



The vagal lobes are large and oval or crescentic in shape. In the 

 carp the facial lobe is not overlapped by the vagal lobes, as it is in 

 the goldfish. In the bream the facial lobe is small and lies further 

 forward than in the other members of the group. In the tench 



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