DEEP-SEA TELEOSTS AND FIERASFER 



169 



occur, a widely modified series of integumentary phos- 

 phorescent organs are often evolved as lures by predatory 

 forms. It is evident, in the case of deep-sea fishes, that 

 the simple condition of their structures does not separate 

 them widely in point of descent from more specially 

 evolved Teleosts. Intermediate forms, occurring in shal- 

 lower water, often connect them clearly with different, and 

 widely distinct, groups of bony fishes. In this way the 





Fig. 175. Fierasfer acus, Kaup. X . (After EMERY.) Commensal of sea- 

 cucumber in southern waters. 



forms which are shown in Figs. 172, 173, 174 are severally 

 connected with the cottid, the cod and the salmon, al- 

 though the striking similarity of their outward structures 

 would naturally lead one to regard them as far more 

 intimately related. 



Another interesting instance of the modification of a 

 fish's form by its living conditions has often been noted in 

 the case of Fierasfer (Fig. 175). This small Teleost lives 

 as a commensal in the branchial chamber of the sea-cucum- 



