2 2 Guide to tJic British Fresh- J]\itcr Fishes 



Mediterranean but not the lilack Sea. Eels occur in both fresh 

 and salt water, in the former penetrating to the smallest brooks 

 and ponds, in the latter lurking among rocks and weeds near the 

 shore. They are almost omnivorous, but feed chiefly on small 

 fishes, crayfishes, worms, etc. ; they are nocturnal, in the day 

 usually hiding in holes or lying buried in sand. jNIale Eels rarely 

 grow to more than 20 inches long, but females grow much larger, 

 especially in the fen district, where a length of over 5 feet and a 

 weight of 20 lbs. or more may be reached. It is now established 

 that the Eel breeds only once in its life. Towards the autumn a 

 certain number become silvery and migrate to the sea and make 

 their way far out into the Atlantic ; their breeding place is in deep 

 water, probably south of the Azores. The transparent strongly 

 compressed larvae (Leptocephalus) are quite imlike the adult ; 

 when about 8 inches long they cease feeding, and during their 

 migration towards the coasts and rivers, which occupies several 

 months, they shrink both in depth and length, until they become 

 little Eels, or Elvers, about 2^- inches long (fig. 13). A series 

 illustrating the metamorphosis of the Eel is exhibited in the case 

 entitled " Fisheries Investigations " on the left of the staircase in 

 the Central Hall. Tlie Eel exhibited is from the Thames at 

 Teddington ; it measures 35 inches, and may have weighed from 

 4 to 5 lbs. 



CYPRINIDAE. 



This large family of strictly fresh-water fishes inhabits Europe, 

 \sia, Africa and North America. All or most of the fin -rays are 



flexible and jointed, and the pelvic fins 

 are abdominal in position ; there is no 

 adipose fin ; the mouth is toothless, 

 protractile, and l)ordered above by the 

 praemaxillaries only. 



The pharyngeal bones, a pair of 

 bones that lie in the throat just behind 

 the gills, bear a small number of teeth 

 that bite upwards against a hard plate 

 supported by a process from the skull. 

 In a wall-frame are exhibited the 

 pluiryngeals of some British species, 

 to illustrate tlie ditterences in the form, number and arrangement 

 of the teeth. 



Fig. 14;. — Pharyngeals oi' 

 Chdb. 



