IDakin and Latarchk — The Plankton of Lough Neac/h. 



63 



Wesenberg Lund has been foremost in the discussion and investigation of 

 the temporal variation ; and we take from him the classes of form-variations 

 that may be recognized. There are four different kinds — individual variations, 

 age variations, local variations, and seasonal variations. 



Little is known of the two first ; but the latter kinds have now been 

 investigated by a large and ever-increasing number of continental workers, 

 most of whom have associated themselves with some group or genus. 

 Moreover, it is the local and temporal variation which has been responsible 

 for the creation of new species. 



Seasonal variation has been studied by Lauterborn in a quite famous case 

 of the Eotifer Anurea cochlearis. Langhans has treated other species of 

 zooplankton. Wesenberg Lund himself has dii-eeted attention to the Diatoms 

 as well as to most of the other groups of plankton organisms. 



Temporal variation has, in fact, been so far discussed in connexion with 

 the following species : — 



ZOOPLANKTON Cladocera. 



COPEPODA. 

 EOTIFERA. 



DiNOFLAGELLATES. 



Flagellata. 

 PHYTOPLANKTON Uiatomageae. 



Hyalodaphnia. 

 Daphnia (various species). 

 Ceriodaphnia. 

 Bosmina longirostris. 

 Acroperus. 

 Evadne. 

 Podon. 



Cyclops strenuus. 

 Diaptomus gracilis. 

 Anurea cochlearis. 



„ aculeata. 

 Asplanchna. 

 Triarthra longiseta. 

 Notholca. 

 Polyarthra. 



And others. 

 Ceratium hirundineUa. 

 Dinobryon. 



Fragilaria crotonensis. 



Asterionella. 



Tabellaria. 



CycloteUa. 



Stephanodiscus. 



Melosira. 



