A FISH FROM A PELAGIC EGG. 59 



The little fishes at this stage are still more or less trans- 

 lucent, except in the region of the eyes, which are silvery, and 

 on the parts where the pigment occurs. Moreover, their fond- 

 ness for a minute reddish Copepod (Calanus finmarchicus), 

 which occurs in myriads around them, gives the region of the 

 stomach a faint pinkish hue from the translucency of the 

 tissues. Soon, however, pigment appears at first chiefly 

 along the dorsal and ventral margins of the body and, by- 

 and-by, foreshadowing in the cod those peculiar squares which 

 give the sides, at a somewhat later stage, their tessellated or 

 tartan-like aspect. Besides, they are found nearer the bottom 

 of the water, so that they can be captured in a naturalist's 

 trawl with a fine gauze-bag at the end. There is, therefore, a 

 downward tendency as the little fishes get older and stronger, 

 and thus in many cases a parallelism exists between them and 

 the minute forms on which they prey, for on deposition the 

 eggs rise towards the surface, where the helpless larvae (or 

 newly hatched young fishes) also often occur, and then they 

 seek the lower regions of the water as their size increases. 



There is much that is wonderful in such a life-history, 

 especially in the metamorphoses or changes of form undergone 

 by many of our best fishes such as 

 the flat fishes (Pleuronectidre), which 

 come out of the egg just like a 

 haddock or a cod, with an eye on 

 each side, as in Fig. 1, yet in after 

 life have both eyes on the same side. ^ IG 14 Young Lemon .Dab 

 Nothing like this occurs in any of in the third stage, enlarged, 

 the higher vertebrates. Gradually 



during growth the body of the fish increases in depth (Fig. 14), 

 then the right or left eye passes over (Fig. 15) the ridge of the 

 head to the opposite side, while the creature, hitherto pelagic, 

 sinks deeper in the water and exhibits a tendency to lie on the 

 side from which the eye has passed, and which gradually loses 

 its dark pigment so as to become white 1 . It finally reaches 

 the bottom, taking up its residence amongst the sand or sandy 

 mud, and lying with the two eyes and the coloured side up, the 



1 The tardy disappearance of the pigment in some forms is interesting. 



