EGGS AND LARV.-E AND THEIR DEVELOPMENT 



103 



the eyes beccming quite black, though the rest of the body- 

 remains very transparent. Black pigment in the eye is necessary 

 for vision. By the time the yolk is all gone, which is about four 

 or five days after hatching, the fin-membranes are somewhat 

 broader, but there are no fin-rays in them, nor any bones in the 

 body. The breast-fin is a rounded flap behind the head, the 

 second pair of side-fins are either small or not yet developed. 



Fig. 57 



Figs. 56-58. — Three stages in the development of the Cod, showing the transforma- 

 tion of the larva into the perfect form. The larva represented in Fig. 56 is 

 a little over i inch in length. At the stage of Fig. 57 the young fish is just 

 I inch long, at that shown in Fig. 58 it is about i § inch. 



At this stage the little fish begins to feed, and the particles it 

 takes are necessarily very small : the food consists of the minute 

 microscopic larvae of shell-fish, worms, and other creatures with 

 which the sea teems. It is interesting to observe in the aquarium 

 that these little fish larvae, minute and delicate as they are, peck 

 at each particle of food in a deliberate and determined manner, 

 and that their food is not carried into them automatically. They 

 see each particle before they seize it, and snap at it by curving 



