BY CRAB-LIGHT. ^ 77 



A. M. Norman, naturalist of the " Porcupine," the crustacean 

 being Ethusa granulata : " The examples at one hundred and 

 ten to three hundred and seventy fathoms in the more south- 

 ern habitat have the carapace furnished in front with a spinose 

 rostrum of considerable length. The animal is apparently 

 blind, but has two remarkable spiny eye-stalks, with a 

 smooth rounded termination where the eye itself is ordinarily 

 situated. In the specimens, however, from the north, which 

 live in five hundred and forty-two and seven hundred and 

 five fathoms, the eye-stalks are no longer movable. They 

 have become firmly fixed in their sockets, and their character 

 is quite changed. They are of much larger size, approach 

 nearer to each other at their base ; and, instead of being 

 rounded at their apices, they terminate in a strong rostrate 

 point. No longer used as eyes, they now assume the func- 

 tions of a rostrum ; while the true rostrum, so conspicuous in 

 the southern specimens, has, marvellous to state, become ab- 

 sorbed. Had there been only a single example of this form 

 procured, we should at once have concluded that we had 

 found a monstrosity ; but there is no room for such an hypoth- 

 esis by which to escape from this most strange instance of 

 modification of structure under altered conditions of life. 

 Three specimens were procured, on two different occasions^ 

 and they are in all respects similar." 



Specimens of these crabs found in shallow water had per- 

 fect eyes ; but, beyond one hundred and ten fathoms, they had 

 changed as above stated. As Darwin has said, the stand for 

 the telescope is there, though the telescope with its glasses 

 has been lost. 



Probably many of the deep-sea forms are luminous in 

 some way.*** Aristeus and allied forms are known to have 



