made during the Voyage of H .M.S. * Challenger? 579 



which goes to considerable depths. This one, however, was brought up 

 only later. 



Everybody who for some time has been in the habit of visiting the 

 fish-markets of the Mediterranean knows how great a rarity the " gre- 

 nadier-fish" (Lepidoleprus or Macrurus) is considered to be by the fisher- 

 men of those shores, and how little was known as to where those curious 

 Scopelids Sternoptyx, Chauliodus, and others might live. The latter are 

 washed on shore from time to time, aud are sure to come into the hands 

 of naturalists, as the fishermen know their value. In the Italian fish- 

 markets they were all the more eagerly looked after, as Professor 

 Leuckart had described in them a sort of sense-organs running along 

 both sides of the body, which he considered, with some doubt, to be 

 organs of sight. But the supply was scanty, and very few zoologists who 

 paid a visit to these places were able to get them. 



Now these riddles are solved ; for we know that Macrurus is one of the 

 commonest inhabitants of the depths, and that with them the Sterno- 

 ptychidae very generally come up. Like other deep-sea animals and those 

 specimens which from time to time were washed on the shores of Italy 

 and Madeira, we have also found them occasionally floating about on 

 the surface of the sea; and one species, a small, elongate, blackish fish, 

 at least seems to belong to the pelagic fauna ; but the majority, especially 

 Stemoptyx and Chauliodus, are so rarely got on the surface, and so con- 

 stantly brought up from greater depths, that I must regard them as 

 inhabitants of that zone. 



One of the Scopelids which came up from great depths (1600 and 

 1900 fathoms) in the Atlantic is very peculiar for its blindness and its 

 flattened head, on the top of which there is a peculiar sense-organ of a 

 silvery colour, 10 millims. long and 9 millims. wide. I examined this 

 organ at that time with a lens, and it seemed to me to consist of three 

 layers : — 1, a very thin transparent epidermis ; 2, a layer of hexagonal 

 small columns resembling in miniature the lateral electrical organs of a 

 Torpedo ; and 3, a silvery tapetum. Without giving any opinion about 

 the nature of these peculiar organs, I should like to point out the analogy 

 which seems to me to exist between them and those organs which Ley dig 

 has figured from the scales of certain Eeptilia in Max Schultze's 'Archiv,' 

 1873. 

 . This fish was afterwards also got in the Pacific. 



Of the other inhabitants of the depths (the Ophidiids, Lophioids, &c.) 

 I have little to say, especially as, after our leaving the Atlantic, these 

 fish were preserved in the upper-deck laboratory, where I have only seen 

 but never studied them. 



Surface of tlie Atlantic. 

 Only a few of the Atlantic surface-animals have been worked out by 

 me ; and about them I shall say a few words when discussing their rela- 



