174 



Mr. W. West and Dr. G. S. West. 



[Oct. 30, 



The Capel Curig lakes merit special mention. The summer plankton is 

 almost a pure Desmid-plankton, and consists largely of those rare and 

 handsome species which are almost exclusively confined to the west-coast 

 districts of the British Islands. The following species occur in great 

 abundance : — Micrasterias radiata, Staurastrum anatinum, St. arersum, 

 St. Arctiscon, St. Cerastes, St. longispinum, and a stout variety of St. Ophiura. 

 It is interesting to note that St. anatinum is present in prodigious abundance, 

 as it was from the littoral region of this lake, near the outlet, that it was 

 originally described. Micrasterias radiata exists in myriads in the plankton 

 of this lake, occurring in a profusion unknown in any other of its British 

 localities. 



Mixed with the Desmids are numbers of Ceratium cornutum, and a very 

 few individuals of Tabellaria fenestrata and T. flocculosa. 



Of a total of 162 species observed in the Welsh phytoplankton, 624 per 

 cent, were Desmidiacese, 11*1 per cent. Bacillarieee, and 7'4 per cent. 

 Myxophyceee. 



VI T. The English Lake-aeea. 



Plankton collections were made from 18 of the English lakes in June, 

 1903, and September, 1906 ; and since then periodic collections have been 

 commenced in Windermere, Ennerdale Water, and Wastwater.* 



As in the Welsh lakes, the phytoplankton of the spring and summer is 

 essentially Chlorophyceous, and contains numerous Desmids, but although 

 most of the typical British plankton-Desmids occur, they are not represented 

 by so many species as in the Scottish or Welsh lakes. The most frequent 

 are the spiny species of Staurastrum, St. lunatum, var. planetonicum, 

 St. Arctiscon, Xantliidium antilopaium, Cosmarium subtumidum, var. Klcbsii, 

 and Sponclylosium pulchrum, var. planum. The presence of Staurastrum 

 Ophiura in the plankton of Easdale Tarn is particularly interesting, as this 

 Desmid is not known to occur in any of the bogs of the English lake-area. 



The Protococcoideae are somewhat scarce, Glceocystis gigas and Sjjhatrocystis 

 Schroeteri being the only generally distributed species, and these only in 

 small quantity. 



The Bacillarieee and Myxophyceee are represented by relatively few species, 

 but in some of the lakes Diatoms are dominant constituents of the plankton. 

 Particularly is this the case in Ullswater, in which Astcrionella formosa 

 was the dominant constituent of both the May and September plankton. 



* As no work has previously been done at the plankton of the English lakes, only the 

 list of species is given for comparison with those of the other British lake-areas. The 

 details of the investigations are reserved for special publication. 



