GENERAL BIOLOGY 711 



(single or double) on this Chart represent the regions where the 

 Salpse occurred. As will be seen, up to the end of May the 

 Salpae were limited to the Atlantic, where the northern boundary 

 was found on the voyage of the ' Thor ' southwards to lie to 

 the west of the Hebrides, and absolutely none were found in 

 the Norwegian Sea or North Sea. Towards the end of July 

 the conditions had quite changed, a fact of which I was able to 

 convince myself on a cruise from Scotland to Bergen and from 

 Bergen to the Shetlands, the Faroes, and Iceland. From the 

 chart, on which the places where we found the Salpae are 

 marked by black spots, we see how the northern boundary has 

 moved to the east and north. Thus a large tongue of the 

 Salpae had pushed its way north of the British Isles in a north- 

 easterly direction, far towards the Norwegian coast, and in a 

 northerly direction we see now that the Salpae reached as far as 

 north-west of the Faroes. And it was not a matter of small 

 quantities. Thus at our station (Station 121, 1905) north of the 

 Shetlands we took many hundred litres per half-hour haul ; and 

 in the quiet, calm weather we could see under the clear surface 

 how the water was quite thick with the Salpae which occurred 

 here and, it is to be remarked, over small depths (less than 200 

 metres), along with other distinctly Atlantic oceanic forms, in 

 almost as large quantities as we had found them anywhere, 

 even in the Atlantic over deep water where they really belong. 

 At the end of August, when the 'Thor' was coming south- 

 wards from Iceland, the northern boundary had moved some- 

 what, yet not very much. We see also that the south-eastern 

 boundary in the North Sea had spread out farther, correspond- 

 ing to a greater development of the large tongue in July." 



Similar experience has also been gained during the 

 Norwegian investigations. Thus in the survey of the " Michael 

 Sars " investigations on pelagic organisms in the years 1900- 

 1908, Damas writes as follows: — 



" In the middle of the summer the invasion of oceanic forms 

 from the Atlantic commences in the Faroe-Shetland channel. 

 There we find an imposing array of species that are entirely 

 absent from the Norwegian Sea, and that certainly do not 

 belong to the fauna appropriate to that sea-basin. Among the 

 most characteristic we may name : Lepasfascic2ilaris,Physophora 

 borealis, Cupulita sarsi, Sohiiaris coj'ona, Salpa fusij^ormis, 

 S. i^iincinata, and ^. irregularis, Arachnactis albida, Clio 

 pyrarnidata and C. tmcinata. These forms do not enter en bloc, 

 and the water-masses which convey them do not seem to have 



