BARRACUDAS, REMORAS AND OTHERS l8l 



following manner : The fish surveys the ground and receives 

 a sensory stimulus through the eyes, which is transmitted to 

 the brain ; from there another impulse is sent out to the 

 muscles controlling the chromatophores, and by the contraction 

 of, say, the red and orange cells here, and the expansion of the 

 brown and black there, the appropriate shade or pattern is 

 acquired. It cannot be said that the fish consciously imitates 

 the surroundings, the whole process partaking of the nature 

 of a series of reflex actions and being accomplished in less than 

 a second. 



Breeding takes place from May to July, at least in the 

 eastern Atlantic. The roes 01 a ripe female Halibut are of 

 relatively enormous size, those of a fish of 350 lb. each being 

 about 2 feet in length and together weighing more than 40 lb. 

 Each, ovary may contain upwards of 2,000,000 eggs, each of 

 which when ripe is only about £ inch in diameter, and about 

 32,000 eggs make up a quart. They are of the buoyant type, 

 and are shed and fertilized in the open sea. 



As in all Flatfishes, the larval fish undergoes a meta- 

 morphosis, which is not only very remarkable in itself, but 

 throws considerable light on the evolutionary history of the 

 group. The eggs hatch after a few days, and the larvae are 

 at first quite symmetrical, and have one eye on either side of 

 the head just as in any other fish. They swim about at the 

 surface of the sea, and, in the case of the Halibut, seem to be 

 carried by the currents towards the inshore waters. After 

 a time one of the eyes (the eye belonging to the future blind 

 side of the fish) moves round over the edge of the head, until 

 it finally comes to lie close to its fellow of the opposite side ; 

 at the same time the dorsal fin, which at first begins behind 

 the head, is prolonged forward, and as soon as the eye has 

 moved round to its final position the fin grows along the edge 

 of the head above it. While these important changes are 

 taking place the little fish sinks to the bottom of the sea, and 

 thenceforward lies with the eyed side uppermost ; at once 

 pigment-cells commence to develop on this side of the head 

 and body. After this stage growth appears to be rather 

 slow, and it has been estimated that a Halibut 4 feet long is 

 about twelve years old. 



It is a well-established fact that in many animals the various 



