148 THE STORY OF FISH LIFE. 



adequately expressed by numbers, they were 

 caught by cart-loads. As these shoals were 

 passing us for a week, with their heads directed 

 up channel, we had the opportunity of noticing 

 that feeding-time was morning and evening. 

 They were pursuing the fry of the herring, and 

 I found their stomachs constantly full of them." 



Another form of sporadic migration, and less 

 mysterious, is that of some of the South American 

 cat-fishes, which appear to possess a remarkable 

 power of anticipating disasters. For they have 

 a " habit of travelling during the dry season, 

 from a piece of water about to dry up, in quest 

 of a pond of greater capacity. These journeys 

 are occasionally of such length that the fish 

 spends whole nights on the way, and the bands 

 of scaly travellers are sometimes so large that 

 the Indians who happen to meet them, fill many 

 baskets of the prey thus placed in their hands. 

 The Indians supposed that the fish carry a supply 

 of water with them, but they have no special 

 organs, and can only do so by closing the gill 

 openings, or by retaining a little water between 

 the plates of their bodies." 



The Indian serpent-head (Ophiocephalus) can 

 travel considerable distances over moist ground, 

 progressing in a serpentine manner, by means of 

 their pectoral and tail fins. 



It sometimes happens that fish are forcibly trans- 

 lated from one place to another by floods, for in- 

 stance, and manage to establish themselves in their 

 new conditions and thrive. In this way many 

 isolated pools and lakes may have been peopled ; 

 often with forms not naturally to have been expected 



