236 SALT-WATER FISHES 



in captivity, at both Piel and Plymoutli,* and the eggs are 

 deposited one at a time. It is also noticed that the extrusion 

 of the eggs takes place earlier in the day as the weather grows 

 warmer. The larva, which (at a temperature of 48" to 

 50° F.) hatches out about the tenth day, measures about 

 \ in. or rather more, and has a large amount of pale orange 

 colouring. As in other flat-fish, there is an air-bladder in the 

 youngest stages, and Cunningham says that it has already 

 disappeared in fish of about f in., or two months old. The 

 same author refers to the constant risk of confusion between 

 these very small soles and the little solenette, the smallest 

 member of the group, which is described below. The sole 

 at the end of its first year measures as much as 6 in. or 

 even rather more. 



The migrations of the sole, as of so many flat-fish, may in 

 all probability be regarded as being restricted to a general 

 movement to deeper water during the extreme cold of winter, 

 and possibly also a food-migration into the shallows in summer 

 time. This would not, however, include the spawning fish. 



Professor Mcintosh describes the egg of the sole as hardy 

 and the larva as extremely active, and he attributes the strange 

 fashion in which the latter rushes about in its tank to the needs 

 of respiration, for he has observed that it darts about open- 

 mouthed. This, he rightly points out, need not be the habit 

 of the little sole in the open sea, but is simply a habit acquired 

 in confinement and necessitated by the absence of invigorating 

 currents in the tank. The breast-fins, he says, vibrate like 

 those of the sea-horse, and there is also rapid movement in 

 the tail. 



As a single instance of what may be done by transplanting 

 sea-fish from characteristic localities to those in which they 

 were either rare or altogether unknown, f it may be mentioned 



* See an interesting account of this by Mr. Butler in tiie Journ. 

 Mar. Biolog. Assoc, September, 1895, p. 3. 



t See also Mr. R. B. Marston's remarks in Chapter X\'I. 



