198 



FISHES FOR MARINE AQUARIA. 



its peculiar organs illustrates to us the ease with 

 which nature sometimes modifies, transforms, and 

 specially adapts one part of the animal frame to an 

 extraordinary use. The back or dorsal fin in fishes 



Fig. 131. 



Angler Fish (Lofihius piscatorius). 



is usually supported by fin rays. Not unfrequently 

 one or more of these is larger than usual (as in the 

 dragonet and weever), and then becomes a weapon of 

 offence or defence. But in the angler fish, the first 

 three spines are modified into long tentacles, and 

 removed from the back to the head (see Fig. 131). 



