THE BREATHING APPARATUS, ETC., OF FISH 27 



hooked. That headlong flight of the trout implies no bodily 

 pain ; but if the fish had previously been hooked, the resist- 

 ance offered by the rod and line would cause the said flight to 

 assume the appearance of a series of struggles, as if the creature 

 were in physical agony. My own belief is that the suffering 

 caused by capture with hook and line is not one whit more 

 severe than that effected with the net ; but, after all, it must be 

 left to physiologists to estimate the acuteness of sensation in 

 cold-blooded animals, lowest in the vertebrate scale. This much 

 is certain : that, as a rule, fish are quickly sensible of anything 

 touching the skin. This is important to their protection from 

 the attack by predaceous species, to which most of them at some 

 or all periods of their lives are constantly exposed. 



In some species special organs of touch have been de- 

 veloped, such as the barbules which depend from the lips of 

 the carp, the barbel, the loach, the sturgeon, and many 

 others. These appendages are exceedingly sensitive, and are 

 used by these fish as feelers, in pursuit of food. In man, the 

 extremities of the anterior limbs have become specialised as 

 organs of touch ; but the homologues of these limbs in fish 

 the pectoral fins do not generally seem adapted for this 

 function, although in the gurnards some of the rays, sepa- 

 rated from the fin and well supplied with nerves, suggest 

 the office of fingers or feelers. 



The visual powers of fish offer a subject of much interest, 

 not only to the angler, whose purpose it is at once to excite 

 The sense and delude them, but to every observer of nature, 

 of sight, because the sense of sight is that which appears 

 to have received in fishes a higher development than any 

 other. The first peculiarity apparent in a fish's organ of 

 sight is the total absence of a true eyelid. Some marine and 

 exotic species, indeed, as well as the British shad, can extend 

 a fold of skin over the eyeball from the posterior and anterior 

 parts of the orbit, leaving a vertical transparent slit over 

 the pupil ; but, with this exception, none of the fish of our 



