91 



and about half this in depth, it is often found actually in the 

 breaking surf, and the curious spectacle may often be seen of 

 an angler with rod and line procuring these large fish from the 

 breakers among the rocks or even along a sandy beach. Its 

 structure and habits, as observed in the aquarium, show how 

 admirably adapted it is to this habitat. In shape it is laterally 

 compressed and comparatively short, in contrast to its marked 

 elevation of body, a feature which doubtless suggested its 

 resemblance to the old high and stately Spanish galleon. It 

 usually moves about the tank in a deliberate fashion, and the 

 facility with which it can turn sharply round is very striking. 

 The significance of the short high body becomes apparent 

 when the fish is alarmed or rushes about after food ; then, 

 apparently with one or two undulations of its flat and powerful 

 body, it passes like a flash across the tank, turning sharply 

 with hardly any evident checking of its speed. It has been 

 suggested that the flattening of the body from side to side as 

 shown typically in the " John Dory " {Zeus), is an adaptation 

 to escape observation, as, when looked at from in front, the 

 body is rendered less conspicuous. Though two species of 

 Dory occur in South Africa {Z. capcnsis and Z. japonicus), no 

 opportunity has been obtained of observing this effect in these 

 forms. In the case of the Galjoen, however, any advantage 

 that may be derived by an apparent diminution of the real size 

 of the body by this means seems to be more than counter- 

 balanced by a side view. It appears rather that the flattening 

 of the body from side to side is an adaptation by means of which 

 the fish can make a sudden and rapid movement, which can 

 also be as quickly checked and changed, a matter of the greatest 

 importance in large fish of the littoral zone, and this may be 

 in part at least an explanation of the general flattening of the 

 body in most cases where, as in large shore forms particularly, 

 a rapid and changing rather than a sustained flight is an 

 advantage. 



A further adaptation to its particular mode of life is observed 

 in its ability to change its colour. It is usually of a dark 

 colour when caught, but, if placed in a shallow, sandy pool, 

 it quickly assumes a very light shade. Specimens, which have 

 been transferred to a well-hghted tank with white enamelled 

 tiles, quickly change from their original dark to a white silvery 

 colour. Mr. Brooking, of East London, writes me that he has 

 observed a very marked and rapid change of colour in the 

 Galjoen, which, after being caught, he put into a pool with a 

 white sandy bottom, and then into one with a dark bottom, 

 the fish rapidly assuming the ground colour when placed in the 

 one or the other. 



[C.P. 6-'i4.] H 



