19 



Greeuland; but tlie lalter is too insufficientl}' known to be ideutified with 

 certaintj'. I think it is best therefore, provisionally, to give it a new name. 



Then follows CJiætoceros diadenm and sociale with maximum (and resting- 

 spores) iii April; Slæletonema costattim, which seems to vegetate in great masses 

 till ti little after midsummer; somewhat later Ch. debile, which in October 

 forms the main mass of the plankton. CIi. contortum, which in July is a cha- 

 racter-form, is not yet found in April in greater quantities. All these species, 

 which occnr in the Limfjord in considerable numbers, are very widely distri- 

 buted, with the exception of Lauderia cystifera; most of them are found, for 

 instauce, on the shores of Greenland and at Lofoden, where I never found the 

 commonest Skager Rack forms, such as Ch. constrictitm, curvisehim, Schiittii, or 

 Leptocylindrus danicus. 



Of oceanic forms a few are also found; these are' very hardy, and can 

 live nearly everywhere, particularly Thalassiothrix Frauenfeldii and Chmtoceros 

 horcule. They differ from tlie neritic forms by not forming resting-spores 

 under unfavourable conditions; they eitlier die or eontinue to live in quite 

 small quantities. Siogle specimens of these species seem to occur nearhj every- 

 where in the sea, as well in the open ocean as along the shores.« 



It might appear from table IV as if, in May and June, unusually great 

 masses of water had come in from the North Sea, with North Sea plankton 

 in predorainant quantities, which had supplanted the neritic plankton which 

 otherwise belongs to the Limfjord; but the salinity, which is measured b}' the 

 Meteorological Observatory at Oddesund, does not seem to indicate this. Pos- 

 sibly there is every year such a period at midsummer; future investigatious, 

 liowever, must prove that. In order to give the most uecessary data for the 

 cousideration of tliis question from a hydrographic point of view, I shall state 

 here from »Meteorologisk Aarbog« the measurements from Oddesund in 1896 

 and 1897, expressed in mean numbers for the various months. 



Salinity at Oddesund, in 1896. Monthly means in p. et. 

 Jan. Febr. Jlarch. April. ^lay. June. July. August. Sept. Oct. Nov. Dec. 



2iS7 <^iO:i ^-m; 3i02 '''ON ^:IK ^!22 3, 05 3,1,; 2,;,,, 2,c,i 2,B3 



and Temperature in "C. (Monthly means.) 

 1,0 3,0 3,0 7,1 12„; 17,.2 17„ 16,, 14,, 10,i 5,., l,i. 

 Salinity at Oddesimd, in 1897. Monthly means in p. et. 



2„, 2„, 2,-, 2,„ 2„, 2„o 2,,, 2,„ 2.,, 2.,,, 

 and Temperature in " C. (Monthly means.) 

 O,., U,. 3,j 6,, 11,., 16,7 17,,, 18,, 13,j 9,,,. 



