IVes^ : Phytoplankton of English Lake District. 1 89 



spicuously abundant : — Xanthidium suhhastiferum var. Murrayi, 

 Staurastrum curvatum, and St. paradoxum. The amount of 

 Ccelosphcerium Kiitzingianum has greatly diminished. Fewer 

 specimens of Ceratium hirundinella, but an increasing amount 

 of Mallomonas longiseta. Rotifers numerous. 



December 1907. — Water-temperature 3.2°C. (=38°F.). A 

 mixed plankton much less in general bulk than in the preceding^ 

 months. Asterionella gracillima in great abundance, but 

 Tahellaria fenestrata var. asterionelloides has almost disappeared. 

 Mallomonas longiseta reaches its maximum abundance. The 

 rest of the phytoplankton has much diminished, although 

 several Desmids are present in small quantity. Peridinium 

 Willei is exceedingly rare, and Ceratium hirundinella has com- 

 pletely vanished. Crustacea present in considerable numbers, 

 but Rotifers are few. 



January 1908. — Water temperature i.i°C. (=34°F.). As- 

 terionella gracillima still very abundant. Few specimens of 

 Mallomonas longiseta. Several species of Desmids (of which 

 Staurastr^im jacu'iferum is most noticeable), not uncommon. 

 One specimen of Pediastrum glanduliferum was observed, doubt- 

 less washed into the plankton from the shores. Crustacea 

 fairly common, but Rotifers scarce. 



February 1908. — -Water-temperature o.2°C. (= 32.5°F.). 

 Very little phytoplankton, but a fair number of Crustacea. 

 Asterionella gracillima somewhat less abundant, but still 

 numerous. Melosira granulata beginning to get conspicuous. 



March 1908. — Water temperature o.4°C. (=33°F.). Crus- 

 tacea dominant, but the whole plankton of little bulk. Melo- 

 sira granulata is more abundant, but the numbers of Asterionella 

 gracillima have very greatly diminished. A few specimens of 

 Tabellaria fenestrata var. asterionelloides, and also of Mallo- 

 monas longiseta, were observed. 



April 1908. — Water-temperature i.7°C. ( = 35°F.). Melo- 

 sira granulata abundant and Asterionella gracillima fairly 

 common. A number of littoral species of Diatoms washed 

 into the plankton. Several species of Staurastrum represented 

 by few specimens. Two spring forms — Uloihrix zonata and 

 Synura uvella — were not uncommon. 



May 1908. — ^Water-temperature 4.4°C. (=4o°F.). An 

 Asterionella-^Xznkion with a fair quantity of Melosira granulata. 

 Rhizosolenia morsa not uncommon, and a little Tabellaria 

 fenestrata both in the typical chain disposition and in the star- 



igog May i. 



