32 COLIN CLOUT'S CALENDAR. 



(about which it is only possible here to speak negatively) 

 do not lead one to suppose that sight is a sense of much 

 practical value to the sharks and rays. There are other 

 classes of fish, however, in which sight seems to play 

 a far more important part, and here it is perhaps 

 possible to institute some rough comparison as to rela- 

 tive perfection with the case of the human eye and 

 brain. 



The class of fish in which the eye is apparently best 

 developed is that of the teleosteans, to which belong the 

 perch, salmon, cod, sole, turbot, and generally speaking 

 almost all the best-known and edible species, including 

 the trout of Yenlake. These fish are comparatively late 

 arrivals in our oceans and rivers, when we judge by a 

 geological standard ; but they have rapidly lived down 

 the great ganoids which preceded them, and have reduced 

 the shark family and the lampreys to a few predatory or 

 parasitic species. Externally and structurally they differ 

 in many particulars from all the other classes of fish, 

 which are now represented only by a relatively small 

 number of survivors ; but on the psychological side they 

 differ most conspicuously in this particular that, while 

 the remaining ganoids, sharks, and lampreys all show 

 signs of depending mainly upon smell, their modern 

 superseders show signs of depending mainly upon sight. 

 The eye of these fishes is large and fairly developed ; the 

 optic nerves are big, and arranged in the same manner as 

 among the higher animals ; and the optic centres form 

 by far the largest portion of the brain. On the other 

 hand, the olfactory nerves and centres are small and 

 shrivelled. The indications of habit are certainly rather 

 inferential, yet they all point in the same direction aa 

 these structural facts. 



Most common fish certainly find their food mainly by 



