THE ABYSMAL ZONE LIFE IN DEEP WATER 



443 



the head and body, but the use of these can only be conjectured 

 in most cases. In some of the Deep-Sea Anglers (e.g. Melano- 

 cetus Murrayi) a luminous knob at the end of the "lure" almost 

 certainly serves the purpose of attracting prey (see vol. ii, p. 85). 

 The bodies of these abysmal forms are of great fragility, and 

 there is a deficiency of lime in their skeletons. Huge mouths, 

 provided with formidable teeth, associated with swallowing powers 

 of no mean order, distinguish many species, giving them a hungry 



Fig. 1296. Blind Deep-Sea Fishes, i, Typhlonus nasus; 2, Ipnops Murray!; 3, Aphyonus gelatinosus. 



and ferocious appearance, and suggesting that no chance of a 

 square meal is let slip. In the manner of sight there are startling 

 differences which at first appear difficult to reconcile. In most 

 cases the eyes are either large and owl-like, serving to catch the 

 faintest rays of light, or else they are degenerate, sometimes, 

 indeed, having entirely disappeared (fig. 1296). It is usually 

 supposed that those fishes descended from ancestors which ex- 

 changed neritic for abysmal life with sufficiently plastic eyes, so 

 to speak, to render their adaptation to the new conditions possible, 

 have gradually acquired exaggerated positive characteristics, while 

 the blind or purblind forms have taken origin from ancestors in 



