GROWTH, MIGRATIONS, FOOD AND HABITS 1 33 



is provided with special organs of touch on the lower side of its 

 head, and also has an acute power of smell. It hunts for worms 

 or shrimps by tapping the ground gently with the side of its 

 head. The eyes are only of use to see enemies above it, and 

 although in the aquarium it acquires in time the habit of rising 

 from the ground and taking worms as they fall from above, it 

 finds difficulty in .seizing them before they reach the bottom. 

 Yet with all this provision for concealment, of no use in obtain- 

 ing food, we do not know at present that it is a much persecuted 

 fish. Future examination of the food of predaceous forms, 

 perhaps of skate and angel rays, may show that the sole has as 

 much to fear as its concealment would indicate ; it has been 

 found in the stomach of the angler. 



The plaice, although it buries itself at times, feeds principally 

 in the daytime and on shell-fish. It has a special crushing mill 

 for these in its throat. Nearly all fishes have teeth in the throat 

 on certain bones belonging to the gill apparatus, and these teeth 

 are usually sharp, but in the plaice they are broad and rounded, 

 and crush shells with great ease. Similar teeth are found in the 

 jaws of the cat-fish, which feeds on crustaceans and shell-fish. 



The mode of hunting of the angler and John dory have not 

 yet been mentioned. The former has special provision for con- 

 cealment and has huge jaws, the lower of which projects beyond 

 the upper. The spines of the first dorsal fin are separate, and 

 can be raised into an upright position on the top of the head, the 

 first having a tag of membrane at the end. The fish lies at the 

 bottom, and other fishes appear to be attracted by this tentacle 

 and fall a prey to the angler. The dory swims upright in mid 

 water, and its body is extremely thin from side to side, so thin 

 that when it is directed towards another fish it does not attract 

 notice or create alarm, and the dory is able gradually to approach 

 within striking distance. A fuller account of these two fishes is 

 given in their special histories. 



Among the dog-fishes and skates and rays there are similar 

 diflferences in the habits and food. The spiny dog-fish is a bold 

 strong swimmer which pursues and devours weaker fishes in the 

 daytime ; it persecutes herrings, sprats, mackerel, and whiting, and 

 lives in shoals which are sometimes so large that they seriously 

 interfere with drift-net fishing. The spotted dog-fishes, on the 

 other hand, are nocturnal, and feed chiefly on the lower animals 



