46 Proceecfinxjs of the Royal Irish Academy. 



time when the water attains its highest temperature. During the winter 

 months Anabaena seems to be absent from the Danish lakes altogether. 



Anahacna spiroides is the only species recorded from the watei's of the 

 Illinois by Kofoid, whei'c it occurred in the water-bloom from June to October. 

 The data were insufficient for determination of maximum. 



Gomphosphaeria Naegeliana (linger) Leram. 



The species GomphospJiaeria Naegeliaiui (Unger) Lemm. occurs in enormous 

 quantities in the Lough Neagh plankton. It is probably either the Coelo- 

 sphaerium Kutzingianum of Messrs. West or C. Naegelianum Unger of their 

 records. They state, however, that G. Naegelianum Unger is probably only a 

 form of G. Kutzingianiom. They record both, and there seems to be some 

 little confusion about the name of the genus. 



Lemmermann himself has identified our specimens, and states that G. 

 Naegeliana is quite different from C. Kutzingianum. It is, as a matter of 

 fact, a different genus, i.e. Gomphosphaeria. The cells of G. Naegeliana are 

 oblong or obovate, and are fastened at the ends of branched hyaline gelatinous 

 stalks. The cells of the Coelosphaerium Kutzingianum are globose, and 

 there are no stalks. The cells are arranged just within the periphery of 

 the colony. 



Wesenberg Lund only refers to Coelosphaerium Kutzi'iigianum in the Danish 

 lakes ; but we should not be surprised if this is the same as our species G. 

 Naegeliana of Lough Neagh. 



Gomphosphaeriii Naegeliana occurs in large quantities throughout the entire 

 year in Lough Neagh. Its curve shows two maxima. The numbers rise 

 in March, and a small maximum with 1,317,500 colonies (aU catches added) 

 is reached in April. The numbers then fall slightly to about an average of 

 400,000 for the months of June, July, and August, and then an enormous 

 increase takes place. In November the number of colonies in all catches was 

 13,646,500 ; and this maximum lasted throughout December. The maximum 

 in November was responsible for water-bloom and also in September. As a 

 matter of fact during the period September to November, any succession of 

 very calm days brought up the alga to the surface. The lake seemed covered 

 with a green layer blown into long streaks by the wind. Our maximum for 

 Gomphosphaeria seems to be remarkably late. Coelosphaerium is usually 

 recorded for autumn; but Messrs. West give for Loch Lomond August, 

 September, October, and November. In Loch Katrine it appears from their 

 figures to be most common in August and September. It is recorded for the 

 English lakes by Messrs. West (Proc. Eoyal Soc, 1908), but appears to be 



