i8 SALT-WATER FISHES 



is, as a matter of fact, somewhat difficult to determine the 

 exact relative importance of these two senses in any fish. It 

 might, for instance, by means of one of those inferences which, 

 while commonly practised by many, are usually dangerous in the 

 study of natural history, be concluded that the sense of smell 

 would be very slight in fishes gifted with large eyes, and 

 correspondingly acute in fishes with only small eyes. The 

 law of compensation would suggest some such balance of 

 faculties. As a matter of fact, the exact converse is found 

 to be the case in some well-known fishes. Thus, some of 

 the flat-fish {Heterosomatd) have both small eyes and feeble 

 powers of smell, while the better-equipped conger {Conger) 

 has not only very large eyes, but also a very strong scent. 

 Attempts have also been made by ingenious writers to associate 

 large eyes in fishes with a habit of seeking food in the 

 darkness, the argument being that the larger eye would be 

 able to utilise the failing light. The argument is not, 

 however, sound. In the first place, it is not by any means 

 satisfactorily established that the mere size of the eye would 

 increase the power of sight ; and, secondly, even granting 

 that such were the case, the sole, a fish of undoubtedly 

 nocturnal habits, has a smaller eye, in proportion to its size, 

 than perhaps any other fish in our seas. Reference is made, 

 when treating in a later chapter of that sub-order, to a special 

 visual organ in flat-fish, as well as to the curious passage of 

 one eye either over the ridge of the head or through its tissue. 

 The existence of the pineal, or median, eye of fishes, which is 

 doubted by Bashford Dean, is a question involving anatomical 

 considerations that hardly fall within the scope of the present 

 volume. 



The muscular power that enables fishes to use the eyes 

 independently, like chameleons, must be of great use to 

 creatures that have often to keep one eye on their meal and 

 the other on their enemies. 



The eyes of sharks difl^er in many respects from those of 



