270 THE VOYAGE OF H.M.S. OHALLENGEE. 



that on a voyage, during which careful and systematic use was made of the surface-net, 

 pelagic forms would have been captured in large numbers. Such, however, was not the 

 case ; the genus Tremoctopus, for instance, was preserved on only four occasions, Omma- 

 strephes on five, Onychia on six, and Cranchia on three or four. 1 Mr. Murray informs 

 me that this is to be accounted for by the astonishing activity of these animals, which 

 is so great that they were only captured when the vessel was sailing rapidly, a 

 condition in general unfavourable to the use of the tow-net. 



" Professor Steenstrup has divided both the Octopod and Decapod Cephalopoda into 

 two groups, littorales and pelagici, and as in so many other divisions of the animal 

 kingdom, while pelagie forms belong to but few species, each of which has a wide range 

 of distribution, littoral genera are represented by very many species, each confined 

 within a narrow area. 



" The latter portion of this statement was well illustrated by the genus Octopus ; of 

 which almost every resting-place of the Expedition seems to have furnished a distinct 

 type : about twelve of which belong to species hitherto undescribed. The littoral habits of 

 this type are most clearly demonstrated, for out of twenty-eight species collected, sixteen 

 came, not from dredging stations, but from the shore collections ; and of those obtained 

 by the dredge or trawl, only two were found in depths exceeding 500 fathoms, and there 

 is, of course, no conclusive proof that these were actually brought up from the depth 

 reached by the dredge. 



" Indeed the difficulty of deciding whether the dredge really captured at the bottom the 

 animals eventually found in it, or whether they became entangled in it during its upward 

 or downward progress, was felt to be extremely great in the case of the Cephalopoda, for 

 only in one or two instances were such structural peculiarities found as appeared to 

 demonstrate that the animals were really abyssal in their mode of life. 



" Many very interesting species of Sepia were captured ; some of which have been 

 hitherto known only by their shells. All the specimens of this genus brought home by 

 the Challenger Expedition (including some ten new species) were obtained between 

 Stations 163 and 232, that is to say, during the cruise from the eastern coast of 

 Australia through the Malay Archipelago to Japan ; a strong confirmation of the fact 

 that the Indo-Pacific region is beyond all question the metropolis of this genus, for 

 out of some thirty species previously known, no less than twelve are from this portion 

 of the globe, although it has been much less explored than many others. 



" Among pelagic Cephalopods very noteworthy additions have been made to the genus 

 Cirroteuthis, which has hitherto been represented only by comparatively few specimens 

 from the coast of Greenland, the largest being one in the Copenhagen Museum, which 

 does not exceed 18 inches in extreme length. During the cruise in the Southern 



1 Cranchia was very frequently obtained in the surface-nets, but, like many other common surface forms, was not 

 always preserved. — J. M. 



