36 FISHES. 



the water, and able to remain (as it were) suspended in it. 

 Tliis deviation from the typical form may proceed so far that 

 the vertical axis greatly exceeds the longitudinal in length ; 

 generally all the parts of the body participate in this form, but 

 in one kind of fish (the Sun-fish or Orthagoriscus) it is chiefly 

 the tail which has been shortened, and reduced so much as 

 to present the appearance of being cut off. An excessive 

 lengthening of the longitudinal axis, with a shortening of the 

 vertical, occu^'S in Eels and eel-like fishes, and in the so-called 

 Band-fishes. They are bottom-fish, capable of insinuating 

 themselves into narrow crevices and holes. The form of the 

 body of these long fish is either cylindrical, snake-like, as in 

 the Eels and many Codfishes, or strongly compressed as in 

 the Band-fishes {Trichiurus, Begalecus, etc.) It is chiefly the 

 tail which is lengthened, but frequently the head and trunk 

 participate more or less in this form. Every possible variation 

 occurs between these and other principal types of form. The 

 old ichthyologists, even down to Linneeus, depended in great 

 measure on them for classification; but although often the same 

 form of body obtains in the same group of fishes, similarity of 

 form by no means indicates natural affinity ; it only indicates 

 similitude of habits and mode of life. 

 Eye. The external parts of the Head. — The Uye divides the head 



into the ante-orhital and post-orhital portion. In most fishes, 

 especially in those with a comj^ressed head, it is situated on 

 the side and in the anterior half of the length of the head ; m 

 many, chiefly those with a depressed head, it is directed up- 

 wards, and sometimes situated quite at the upper side ; in 

 very few, the eyes look obliquely downwards. In the Flat- 

 fishes both eyes are on the same side of the head, either the 

 right or the left, always on that which is directed towards 

 the light, and coloured. 



Fishes in general, compared with other Vertebrata, have 

 large eyes. Sometimes these organs are enormously enlarged, 



