172 THE OCEAN 



amphipods living in the surface waters the 

 entire head is occupied by the two large eyes ; 

 in certain decapods living in depths less than 

 100 fathoms the diameter of the eye is about 

 one-sixth the length of the carapace, while in 

 those from about 300 fathoms the relation is 

 about one-tenth, and in those from 500 or 600 

 fathoms it may be as low as one-twentieth. 



Peculiar stalked eyes have been observed 

 in a few pelagic larval fishes, but they prob- 

 ably develop into normal eyes during the 

 later stages. A stalk-eyed cuttlefish has also 

 been taken at a depth of 100 fathoms. Tele- 

 scopic eyes are known in fishes from depths 

 less than 300 fathoms, usually such as float 

 rather than swim, and as they point upwards 

 they seem well adapted to receive the faint 

 vertical rays of light. 



It must be pointed out that sometimes the 

 eyes of benthonic animals become larger with 

 increase of depth, and it is possible that this 

 is for the purpose of being sensitive to phos- 

 phorescent light. 



Intermediate Water Fauna. — ^Up to the 

 present time it is impossible to make any quite 

 satisfactory statements as to the distribution 

 of animals living in the great intermediate 

 region between the lower limit of the photic 

 zone and the bottom. While many animals, 

 like some of the Challengeridae among the 



