PEDIGREES. 187 



lineage. They may be traced back as far as the 

 Cretaceous period. Other relatives of the her- 

 rings — the sardine tribe — are also to be traced 

 back to the cretaceous. The sardines are a 

 numerous family. In addition to our familiar 

 little friend of the breakfast table, there are 

 numerous deep sea phosphorescent forms, with 

 which we cannot deal here for lack of space. 

 The herring-like elops, the true herrings and 

 sardines, are the living representatives of a much 

 larger and ancestral stock. The extinct forms 

 all bear a very striking resemblance to modern 

 herrings. To discuss these in cold print were 

 profitless ; but those who have the good fortune 

 to live near great collections of fossil-fishes, such 

 as that of the British Museum, can glean for 

 themselves some very striking lessons in the 

 pedigree of the herring and its kindred. All 

 these forms are grouped together to form one 

 family, the Isospondyli 



As allies of the herrings, we turn now to the eels 

 — a tribe with which we are all more or less familiar, 

 at least with some members. Three well-marked 

 forms are included in this group — the common 

 fresh water and conger eel, the mursenas, and 

 the electric eel. The mursenas are probably but 

 little known to most people. They differ from 

 all the other forms with which they are asso- 

 ciated in their remarkable colouration, which is 

 very brilliant and generally mottled in pattern. 

 The feature which makes the electric eel cele- 

 brated we have already discussed (p. 158). The 

 eels serve as admirable object lessons in the effect 

 of adaptation to a peculiar mode of life burrowing 



