234 A HISTORY OF FISHES 



movements in the water, and thus to avoid obstacles or to 

 detect the presence of their prey. It is of some interest to note 

 that even the species with comparatively well-formed and 

 functional eyes depend very little on the sense of sight to obtain 

 food, and it has been found that if the eyes are removed from 

 some individuals they are able to detect the presence of the 

 prey just as quickly as the normal ones. Further experiments 

 have shown that the senses of smell, taste, and hearing of these 

 fishes are, on the whole, much the same as those of other fishes, 

 and that it is the intensification of the "lateral line sense" which 

 serves as compensation for the loss of sight. 



The suggestion that Blind-fishes were originally carried into 

 the caves by accident, or that individuals without eyes or with 

 relatively feeble eyes arose in the open as mutations or "sports," 

 and by finding their way into caves were enable to survive, 

 may be dismissed as highly improbable. In the case of the 

 Cuban forms it seems likely that they developed along with the 

 caves. Their ancestors, no doubt, lived in the sea among the 

 coral reefs, and may have been left behind in their original 

 habitat, when these reefs were eventually elevated and carried 

 away from the sea, gradually accustoming themselves to a life 

 in fresh water. In all the o.ther Blind-fishes the penetration 

 of the caves must have been a voluntary matter, and in this 

 connection it must be remembered that nearly all are species 

 of a type which might be described as peculiarly fitted to be 

 blind! The Cat-fishes, for example, live mostly in muddy 

 rivers and streams, and depend more on the sensitive barbels 

 than on the eyes in obtaining food. The blind Cyprinodonts 

 must have been descended from the eyed forms belonging to 

 the same family, or at least from some very similar forms now 

 extinct, and these eyed forms already inhabit situations in 

 which the eyes are of little use and are much reduced in size. 

 Further, one of these species is habitually found under stones 

 in small rivulets, and another, which has reached the under- 

 ground streams, has developed ridges of sensory papillae. 



On the whole, therefore, it seems probable that fishes which 

 have elsewhere become accustomed to do without light, and 

 have adapted themselves to such conditions, have voluntarily 

 penetrated into caves, colonising them gradually step by step, 

 becoming more and more specialised for a life in darkness as 

 each successive generation penetrated deeper and deeper into 

 the recesses. All kinds of fishes abound in the so-called twilight 

 regions near the entrances to caves, and some of these might 



