82 — 



The number of hours of bright sunshino during the normal 

 period of occurrence of Anabaena was therefore in 1906 con- 

 sidérable more than in the other twoyears,and this may account 

 for the poor development of this form in 1906. As further évi- 

 dence of the influence of bright sunshine, it may be noticed that 

 whereas in 1907 Anabaena came very rapidly to the front, it 

 did not reach its maximum in 1908 till July. June of 1908 was 

 exceptionally sunny, and this may be the cause of the later 

 dominance of Anabaena in that year. In other words there is 

 some évidence for the view that the représentation of this spec- 

 ies is aclversely affected by unusually bright sunshine. 



Table of occurrence of Anabaena in Bartoris pond, 

 1906-1909. 



Lyngbya versicolor shows cuiitea différent periodicity,being 

 found principally during the last four months of the year (1) ; it 

 was found in some slight amount from August to October 1906, 

 September to December 1907, October and November 1909, 

 while in 1908 it was only scantil)- represented, although soine- 

 what common for a brief period in June. There is no apparent 

 relation to sunshine or sliade in this case, and we do not feel 

 that the data are adéquate to draw any other conclusions. It 

 appears as though this form may hâve occasionally been over- 

 looked in collecting. 



/. — Tue Flagellâtes. 



Three species of Flagellata — Euglena viridis, Trachelo- 

 monas volvocina and T. hispida — play an important part 



(1) This is quite the usual time l'or the appearance ol'Oscillarieae in small 

 pièces ol water {cf. Fritsch and Etich, 1909, pp, 1 1- 45 and Brunnthaler, 1907, 

 p. 195). 



