10 



Caroline L e e g a a r d. 



a 



Fragilaria eijlindrus Grün. 



(Fig. 7.) 



1884 Grunow, p. 55, pi. 2, f. 13. 

 1897 b Gran, p. 20, pl. 1, f. 4—5. 

 1905 Jörgensen, p. 102, pl. 6, f. 9. 

 1908 Gran, p. 115. 



Pragilaria cylindrus occurring constantly with Achnanthes taeniata could be disti- 

 guisbed from the latter by the very narrow linear cells, which are discribed in the 



„Nordisches Plankton". The breadth of the 

 chains according to the Finnish material which 

 has been examined was 14 — 35 </. 



This species was not numerous except at 

 station F 41, occurring here in the upper wa- 

 ter-layers with the maximum number of 268800 

 cells pr. litre at the surface. Farther west in 

 the Gulf of Finland it diminishes, and the 

 maximum is found in the deeper layers (sta- 

 tions F 50 and F 61). In the northern part 

 of the Baltic (station F 74) it occurs only 

 singly; in the Gulf of Bothnia it is wanting 

 at the southern station (P 30), while it is found in small quantifies at the northern one 

 (F 23) with the maximum number of 8600 cells pr. litre at the depth of 30 mètres. 



Fig. 7. Fragilaria cylindrus. 



a. Cells in side-view. 



b. Cell in front-view. 



050 

 1 ■ 



Leptocylinâms minimus Gran. 



(Fig. 8.) 



1915 Gran, p. 72. 



A few chains occurred consisting of narrow cylindrical cells with rounded ends. 

 The contents of the cells were coloured by the fixing-fluid, so that three dark bodies 



Fig. 8. Leptocylindms minimus. 

 1000 



appeared, one in the middle of the cell and one at each end. This indicates, that the 



cells contain two chromatophores connected by a central part with the nucleus. This 



species is very probably the same as the Leptocylindrus minimus of Gran (1915). 



The diameter of the cells was 4 ;j. 



This species occurred singly at stations F 23, F 74 and F 41. 



Tom. XL VI II. 



