314 THE ZOOLOGIST. 



a Cuttle-fish, unfortunately greatly damaged. I was so struck by the 

 singularity of its form and the brilliance of its colour that I at once 

 secured it, and, showing it to the fishermen, asked whether they were 

 acquainted with it. Upon their replying in. the negative, I called their 

 special attention to it, and offered a handsome reward for the next 

 specimen secured, either alive or in good condition, and then passed on 

 to other fishermen and repeated my promise. Shortly afterwards I was 

 summoned, and shown a specimen clinging to the net, which I seized 

 and placed in a vessel of water. At that moment I enjoyed the 

 astonishing spectacle of the brilliant spots which appeared upon the 

 skin of this animal, whose remarkable form had already impressed me; 

 sometimes it was a ray of sapphire-blue which blinded me ; sometimes 

 of opalescent topaz-yellow which rendered it still more striking ; at 

 other times these two rich colours mingled their magnificent rays. 

 During the night these opalescent spots emitted a phosphorescent 

 brilliance which rendered this mollusc one of the most splendid of 

 Nature's products. Its existence was, however, of short duration, 

 though I had placed it in a large vessel of water. Probably it lives at 

 great depths.'" * 



After describing the various luminous organs, Dr. Hoyle remarks : — 

 " The question of the utility of these variously coloured lights to the 

 creature possessing them admits of an answer which is, at all events, 

 extremely plausible. It was suggested in the case of deep-sea fishes 

 by Brauer, and has been adopted by Chun in reference to the Cephalo- 

 poda. They serve as recognition marks by which the various species 

 can identify their fellows ; just as certain colour patches in the plumage 

 of birds enable them to find their mates, so in the darkness of the 

 ocean abysses do these fairy lamps serve their possessors. Another and 

 perhaps even more obvious utility is suggested by the general dis- 

 tribution of these organs. It has been pointed out that they are, 

 almost without exception, on the ventral aspect of the body — that is, 

 the inferior surface in the position in which the animal habitually 

 swims. It must happen, therefore, that when the creature is moving 

 over the floor of the ocean in the quest for food, this must be illumi- 

 nated by its lamps, and the advantages of a series of searchlights 

 playing over the ground will be at once apparent. 



" Finally, we have the question, How is the light produced ? To 

 this we can only say that this is an instance of the transformation of 

 one kind of energy into another. We are quite familiar with the pro- 

 duction of heat in the animal body by the processes of oxidation which 



* The species thus referred to was Histioteuthis lonelliana. 



