236 THE SENSE-ORGANS AND PBROBPTION OP PISHES. 



Eel {Anguilla vulgaris). 

 Three-bearded rockling [Motella 



tricirrata) . 

 Five-bearded rockling {Motella 



mustela) . 



Loach {Nemacheilus harhatula) 

 ? Sucker {Lepadogaster Gonanii) 

 Sole {Solea vulgaris). 

 Little sole {Solea minuta). 

 Sterlet {Acipenser ruthenus) . 



To this list may almost certainly be added the remainder of 

 tbe Raiidse, together with the angel-fish {Bhina squatina) and 

 torpedo. Unfortunately, however, the examples of these forms living 

 in the tanks at Plymouth have never become thoroughly at home, and 

 still (November, 1889) take food reluctantly. In fact, the skates 

 have for many months subsisted entirely on shrimps, and very rarely 

 take notice of other food ; but owing to the kindness of Mr. Wells, 

 tbe superintendent, I had an opportunity of seeing the habits of 

 the skate under more favorable conditions at Brighton. 



Of the fishes in this list the conger, rocklings, sole, and rough dog- 

 fish were the most frequently and minutely watched. 



There are many points of resemblance in the habits of the various 

 animals mentioned above, and some general observations may be 

 made with regard to them collectively before pointing out the 

 special features of interest in the natural history of each. In the 

 first place they are all more or less nocturnal animals, and (? sterlet 

 and Protopterus) remain in hiding by day, many of them being fur- 

 nished with special modes of concealment. For example, the 

 conger and the rocklings live in holes in the rocks, the eel and Pro- 

 topterus in mud, the sucker and the loach under stones, while the 

 sole lies completely buried in the sand_, the eyeballs alone being ex- 

 posed. When left to themselves they getferally lie motionless until 

 dusk, when they begin to swim about with more or less activity. 

 If, however, while they are lying thus bidden the juice of food-sub- 

 stances (such as squid or pilcbard) is poured into the water, they 

 come out and feel about for a considerable time, clearly perceiving 

 the odour. The dog-fish, conger, and eels feel for food with their 

 noses, Protopterus witb its pectoral and pelvic fins, the rocklings 

 with the barbels and pelvic fins, the loach with its bai'bels, and the 

 sole with the villi on the left (lower) side of its head. 



None of these fishes ever start in quest of food when it is first 

 put into the tank, but wait for an interval, doubtless until the scent 

 has been diffused through the water. Having perceived the scent 

 of food, they swim vaguely about and appear to seek it by examining 

 the whole area pervaded by the scent, having seemingly no sense of 

 the direction whence it proceeds. 



Though some of these animals have undoubtedly some visual per- 

 ception of objects moving in the water, yet at no time was there the 

 sbghtest indication of any recognition of food-substances by sight. 



