176 ni?TTTSH DESMTPTArEyfi. 



SCOTLAND. Plankton of Loch Fadasfhoda, Lewis, 



o 



Outer Hebrides! Plankton of Loch Asta, Shetland* ! 



II.-KLAMI. Plankton of Lough Neagh ! 



di'mjr. Distribution.- -QermBxiy. New Zealand 

 (form). 



This variety is sometimes frequent in the freshwater 

 plankton and is the longest known Desmid in proportion to 

 its breadth. 



Borgeson & Ostenfeld (Phytoplankton Faeroes, 1903, 

 p. 620) state that Cl. nul>i>rmium must be placed as a synonym 

 of 67. arictthur. The C!<)*teria recorded b} T these authors 

 from the Faeroes are most probably forms of CL aciculare, 

 but we doubt if either of them have observed any examples 

 of CL *itl>]>}-t>ninn. We have ourselves here placed CL xitl>- 

 jirniiiDH as a variety of Cl. aciciilnrt".^ we think its characters 

 do not warrant its complete separation. 



The var. siibproniim differs from typical CL ncicnlarc in 

 two important points, (1) the median portion of the cell is 

 cylindrical, and (2) the apices are much more produced, being 

 of a uniform thickness with parallel margins, and obtuse, 

 although very narrow at the extremity. The extremities of 

 the cell are produced into long colourless processes such as 

 those found in CL ftrtamtm ; and the apical vacuoles, although 

 containing only one moving granule, are of great length and 

 contained within the base of t>hese processes. 



"67. finl>jiriiiiiiiii var. Ific-nxfir'' Lcmm. (Plnnktonalgen, 

 1899, p. 344, t. 1, f. 13, 14) should be relegated to this variety, 

 although the dimensions are a little larger, length 500-800/1 ; 

 breadth 6-8^. 



50. Closterium Ceratium Perty. 

 (PI. XXIII, figs. 6-8.) 



Closterium Ceratium Forty, Kloinst. Lebonsf. 1852, p. 200, t. 10, f. 21; 

 IlalM-nh. Flor. Eiu-op. Al^ar. Ill, 1808, p. 138; Do Toni, Syll. Alg. 1SS9, 

 1>. s:',7; Liitkom. Desm. Attersees, 189,3, p. 543; Roy & Biss. Scott, 

 Dosm. 1S5)-!., p. 244 ; Nordst. Index Desm. 1890, p. 72 ; Wost & G. S. 

 West, Alffa-fl. Yorks. 1900, p. 56 ; Alg. N. Ireland, 1902, p. 36. 



Arthrodia Ceratium Kuntze, Eevis. gen. plant. 1891, p. 883. 



Cells small, 20-40 times longer than their diameter, 

 straight, slightly curved, or sigmoid, gradually attenu- 

 ated from the middle to the extremities, apices drawn 

 out into very acute, needle-like points ; cell-wall smooth 



