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 
oO gas 
LEE 
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 acommensal in the branchial chamber of the sea-cucum- 
