152 MARINE PRODUCTS OF COMMERCE 



rays, is devoid of color. The upper side is fully pigmented and tliis is where both 

 eyes are located. The young, for a very brief time while in the larval stages, 

 swim upright and have eyes on opposite sides of their head. But very early 

 in life they turn either to the left or right side, according to the species. During 

 this turning process the eye on the lower side of the head "migrates" to the 

 upper side, twisting the skull in the process. This is a wise provision made by 

 nature, for an eye could not serve a useful purpose when buried in sand and 

 mud. Most species of flounders have fairly large mouths, equipped with moder- 

 ately well-developed teeth which adapt them to the life of predators. 



Finally, we may mention the globular fishes as another form that departs 

 widely from the usual. These fishes include the puffers or blowfish, burrfish, and 

 porcupine fish. They have short roundish bodies and are capable of inflating them- 

 selves with water or air, hence becoming globular. As they are not adapted to 

 rapid swimming, they must use their power of inflation for defense, to which 

 further reference is made in another section of this chapter. 



Many intermediate forms exist. The deep sea contains many which have a 

 distinctly bizarre appearance: large heads, large mouths, fanglike teeth, small 

 bodies, long tails, excessively large eyes, stalked eyes, etc. Many deep-sea forms 

 have light organs. When those which have light organs turn on all the lights, 

 they must look like a well-lighted ship at sea at night. Then there is the very 

 oddly shaped ocean sunfish which is so short that it looks as if it were all head, 

 with body and tail missing. This fish, which grows to a weight of a ton or more, 

 is so flat and round that it reminded the scientist who named it of a millstone. 

 Accordingly, he called it Mola mola. 



It is evident from the foregoing paragraphs that fish "come" in many shapes 

 and forms. It is plain, also, that the phrase "shaped like a fish" is not actually 

 descriptive. 



The Body Covering. In the discussions relating to the antiquity of fishes and 

 their shape or form body coverings were mentioned incidentally. It was shown 



{Courtesy U. S. Fish and Wildlife Service) 



Fig. 10-2. Gar (Cylindresteus platestemus) . 



that some of the extinct forms were largely incased in bony shields. One group 

 of living fishes, namely, the ancient fresh-water gars, still retain a fair armor, the 

 head being protected by hard external bones and the body by hard overlapping 

 bony plates (Fig. 10-2). The sturgeons, which, too, are ancient fishes and belong 

 to the ganoid group, have large bony plates in rows that do not cover the body 



