676 



DEPTHS OF THE OCEAN 



Luminous 

 fishes. 



present it is probably impossible to lay down any rules relating 

 to them. 



If we take into account the exceptions here mentioned, we 

 arrive at the result that in the higher groups, viz. squids and 

 fishes, special light-organs are known mainly in oceanic forms 

 belonging to warm areas. 



Among the fishes the luminous forms are mostly found in the 

 families Stomiatida:, Sternoptychidse, Scopelidae, and Ceratiidae. 



Fig. 493. 



1. The largest photophore from the ventral series between the pectoral and the ventral of Cyclothone 



signata, Garm. , and C. signata alba, A. Br. 



2. The largest photophore from the ventral series between the pectoral and the ventral of Cyclothone 



microdon, Giinth. , and C. microdon pallida, A. Br. 



3. The largest photophore from the ventral series between the pectoral and the ventral of Cyclothone 



livida, A. Br. 



4. The largest photophore from the ventral series between the pectoral and the ventral of Cyclothone 



acclinidens, Garm. 



5. The largest photophore from the ventral series between the isthmus and the ventral of Cyclothon^ 



signata, Garm. 



6. The smallest photophore from the ventral series between the isthmus and the ventral of Cyclothone 



signata, Garm. 



7. Reflector cells of a photophore from the ventral series of Cyclothone microdon pallida, A. Br. 



(After Brauer. ) 



After carefully examining the specimens belonging to these 

 groups captured by the " Valdivia," Brauer pointed out that a 

 certain regularity in the arrangement of the light-organs seems 



