12 Caroline Leegaard. 



An auxospore appeared at station F 50 at the depth of 40 inetres. 1t was veiy 

 remarkable in that a thick-walled resting-spore was lying inside the thin-walled auxo- 

 spore. The formations of the auxospore and the resting-spore have in this case developed 

 without any intermediate link of thin-walled cell-generations. The diameter of the cells 

 was 10—23 («, that of the auxospore 25 f<. 



Only at station F 41 in the upper water-layers the chains without resting-spores 

 dominate those containing spores. In the deeper layers we have quite the opposite case, 

 but hère this species is rather scarce. At stations F 50, F 61 and F 23 a few cells 

 without resting-spores occurrerl, wliile the species is totally lacking at stations F 30 

 and F 74. 



This diatom is not particularly numerous at any of the stations. The greatest 

 numbers noticed are 20100 cells pr. litre of the sporeless cells (station F 41, 10 mètres) 

 and 15500 cells pr. litre of the resting-spores (station F 41, 5 mètres). 



The resting-spores were fairly equally distributed over ail the stations in quantifies, 

 which varied between some hundreds and some thousands of cells pr. litre. 



Navicula sp. 



A few chain-forming Navicula-cells were found at some of the stations. On doser 

 examination it appeared, that they belonged to the two species, Navicula Granu and 

 Navicula Vanhöffenii. These two species were not distinguishable from each other, when 

 they were counted. Scattered spécimens occurred at stations F 41, F 50, F 61 and F 23. 



Navicula Grann (Jörgensen). 



(Fig-. 10.) 



1905 Stauroneis Grani Jörgensen, p. 107, pi. 7, f. 25. 



1908 Gran, p. 124. 



1910 Stauropsis Granu Meunier, p. 321, pi. 33, f. 26—27, 33—36. 



The chain in the illustration was found in some intensely heated material from 

 station F 41, 10 mètres. The breadth of the chain, 42 <<, was somewhat smaller than 

 that which is given in the „Nordisches Plankton" (50—57 </); but the plankton-diatoms 

 of the Finnish territory offen being relatively small (a fact which will be discussed låter, 

 page 39) this circumstance need not offer any objection as to the détermination of 

 the species. 



Navicula Vanhöffenii Gran. 



(Fig. 11.) 



1896 a Navicula septentrionalis Cleve, p. 11, pl. 1, f. 9, non Libellus? sep- 

 tentrionalis Ostrup 1895. 



1897 b Gran, p. 21, pl. 1, f. 1 — 3. 



Tom. XLVII1. 



