104 SCIENCE SKETCHES. 



The Common Eel 1 is more or less regularly 

 catadromous. It is doubtless of marine origin ; 

 and the same species is widely diffused in America 

 and Europe, though curiously wanting on our 

 Pacific coasts, as well as in South America. 



The Sticklebacks and the Silversides are sea- 

 shore fishes, the former of cold, the latter of warm 

 regions. Some species of both are now permanent 

 residents in fresh water. The Sticklebacks espe- 

 cially show all degrees of transition, the strictly 

 fluviatile forms being as usual smaller in size and 

 weaker in armature than the marine ones. 



The Pirate Perches and the Elassoma are two 

 very small families, related to each other, and 

 distantly related perhaps to the Sun-fishes. They 

 are probably remains of some older fauna, and are 

 possibly allied to the Berycoids ; but this relation, 

 if real, is not very close. 



The Sun-fishes are peculiarly North American, 

 nothing similar being found in any other region. 

 Their ancestry is probably to be sought among 

 the marine Serranidcz, the large-mouthed Black 

 Bass 2 being probably the member of the former 

 group nearest the parent stock. 



The fresh-water (striped) Bass* are evidently 

 allied to the anadromous members of the same 

 group. 



The Perch family is perhaps originally an off- 

 shoot from the Sea Bass. It has, however, re- 

 ceived a peculiar development in American waters. 



1 Anguilla anguilla Linnaeus. 



2 Microptcrus salmoides Lacepede. 



8 Morone chrysops, mississippiensis, etc. 



