294 



SYSTEMATIC ZOOLOGY 





When small, weighing from five to ten kilos, they are known as 

 chicken halibut, and are especially good. All of these flatfishes 

 live on the bottom, and are interesting because of the curious 

 asymmetry of the head. The body is greatly compressed later- 

 ally, and one side is light in color, the other darker ; the animal 

 lies on its lighter side, and both eyes are on the darker side, the 

 right or the left, as the case may be. The very young flatfish 

 is strictly bilaterally symmetrical, like any other fish, with one 

 eye on each side of its head, and swims vertically in the water. 

 But later it lies on one side on the bottom, and the eve which is 

 beneath slowly migrates until it comes to lie on the same side of 

 the head as the other. In connection with food fishes we should 

 mention the black bass, a fresh-water fish, which has a wide 

 distribution in the United States, and is considered one of the 



finest game fishes. It is 

 confined to America, and by 

 some English sportsmen is 

 considered superior to the 

 trout. 



There remain a number of 

 fishes interesting for some 

 peculiarity of structure or 

 habit. The sticklebacks are 

 small fishes, some marine and 

 some fresh-water, found in 

 both Europe and America, 

 whose chief interest centers 

 in the nest which the male 

 builds for the eggs ( Fig. 301 ). 

 This nest consists of bits of 

 plants which the fish cements 

 together with the secretion 

 from a gland opening just in 

 front of the anus. The nest 

 Fig. 301. Gasterosteus piingitius, the stickle- has two openings, so that the 



back; nest. (After Landois, Hum Claus and fish may gwim through; the 

 Sedgwick's rext-book.) J 



c£^+ are deposited in layers 

 by several females, and the male fertilizes each set as it is 

 laid. 



