44 



Part II, Appendix IV, p. 99, 1905). For the intermcdiate fauna, the term Mesoplankton was proposed. 

 But it was not intended, and indeed it is obviously . not true, that every species may be described as 

 universally epiplanktonic, or as universally mesoplanktonic; a species found among the epiplankton of 

 sub-arctic or of temperate waters may be purely mesoplanktonic at lower latitudes; in the present state 

 of our ignorance the terms can oniy be applied with safety to the date and place at which the species 

 was actually captured, but even in this limited application they have the advantage of brevity, and 

 condense a number of admitted facts. 



Again, it was not intended to imply that the 100 fathom horizon formed a sharp and impassable 

 barrier between two distinct sets of organisms; an epiplanktonic form may descend below 100 fathoms 

 without reaching so far as 250 fathoms ; or, an essentially deep-water species may range up into the 

 epiplankton, and yet not come to the surface; or again, the same organism may range through both 

 epiplankton and mesoplankton. The following instances, taken from among the Chaetognatha, illustrate 

 the use of the terms: 



Species 



Locality 



Range (fathoms) 



Distribution 



serratcdentata 



hamata 



furcata 



kaïnata 



hamata 



Bay of Biscay 

 Faeroe Channel 

 Bay of Biscay 

 Bay of Biscay 

 Siboga area 



o to 100 



o to 500 



o to 200 



2000 — 1500 to 50 



highest capture 533 — 226 



epiplankton 



epiplankton and mesoplankton 



epiplankton and upper mesoplankton 



mesoplankton and lower epiplankton 



mesoplankton 



At the moment this scale seems adequate for a comparison of the vertical distribution of a species 

 at different localities, even though with the increase of our knowledge more precise terms become needed 

 in the future. 



All the hauls containing Chaetognatha which were lowered to a greater depth than 



200 metres (e.xcept 107, Dredge), together with the occurrences of these deeper .species, are 



set out in the table below, which has been extracted from the General Table (j). 28): 



Unfortunately, all these hauls cxcept one (216) were made with open nets; we can 

 therefore at most say with safety that, since macrocephala^ Sibogae, Zetesios and hamata were 



