were, however, counted by a slightly different proce- 

 dure. Exactly 1 cc. from the 20 cc. suspension was 

 measured into a counting cell and all the individuals 

 recorded. From these data the number of individuals 

 or colonies per liter was computed. 



Comparison of the results obtained for those forms 

 caught by both the "1 -liter centrifuge" and the "50- 

 liter net" methods showed that the latter gave the more 

 reliable quantitative data. There were very few spe- 

 cies recovered by the centrifuge which were not also 

 taken in the net. Therefore the net plankton data 

 will be emphasized in the discussion of quantitative 

 distribution. Since the results of the first season's 

 work have already been published (Fish et al. 1929) 

 the present paper will be devoted chiefly to the pre - 

 sentation of the new data acquired in the season of 1929. 



THE SPECIES OF MICROPLANKTON 



Taxonomic investigations of the micro-organisms 

 in Lake Erie began a little more than 50 years ago. 

 Kellicott (1878) in Buffalo, and Vorce (1880-1881) in 

 Cleveland were carrying on simultaneous investigations 

 of the diatoms, algae, protozoa, and rotifers found in 

 the water supplies of their respective cities. New spe - 

 cies of diatoms were described from Lake Erie by 

 H.M. Smith (1878), and Kellicott (1885) published a 

 number of notes on new and rare species of protozoa 

 and rotifers from the waters of the Buffalo region. At 

 about this time appeared Day's "Plants of Buffalo and 

 Vicinity" (1882), a catalog which included records of 

 the observations on cryptogams made by D.S. Kellicott, 

 J.W.Ward, Francis Wolle, and others. 



Additional contributions were made to our knowl- 

 edge of the protozoa and rotifers by Jennings (1894, 

 1900) and Kellicott (1896, 1897). In more recent 

 years Landacre (1908) and Stehle (1923) have published 

 on the protozoa found at the western end of Lake Erie, 

 while Pieters (1902) and Snow (1903) have presented 

 valuable papers on the algae. Not until the present 

 effort in 1929 was an attempt made to survey the micro- 

 plankton throughout practically the entire lake. 



The following list of species includes those organ- 

 isms collected from the regular stations (fig. 1) in the 

 summers of 1928 andl929. Gatherings from the rivers 

 and harbors along the lake shores have not been in- 

 cluded. The majority of species listed are therefore 

 true plankton organisms (euplanktonts), though there 

 are also chance wanderers (tychoplanktonts), and 



those capable of adapting themselves to the plank- 

 tonic existence (faculative planktonts). It is prob- 

 able that the methods employed were inadequate for 

 the catching and identification of the protozoa and 

 rotifers, and for these groups the work of previous in- 

 vestigators is recommended as a guide. The general 

 classification of West and Fritsch (1927) has been 

 followed. 



The following series of symbols has been used to 

 indicate abundance: T, trace; R, rare; C, common; 

 A, abundant; VA, very abundant. 



Isokontae 



Ankistrodesmus falcatus (Corda) Ralfs. (R). Western 



part of the lake. 

 Ankistrodesmus setigerus (Schrftd.) G.S.Wett. (R). 

 Chlamydomonas sp. (T). Shallow water near Buffalo. 

 Cladophora glomerata (Linn. ) Ktltzing. (T). Occurred 



only twice, at surface. 

 Closterium acerosum (Schrank) Ehrenberg. (T). 



Occuned once. 

 Closterium aciculare var. subpronum W. and G.S.West, 



(R). June. 

 Closterium Dianae Ehrenberg. (R). Western end of lake 

 Closterium parvulum Naegeli (R). 

 Closterium Venus Kdtzing. (R). 

 Coelastrum microporum Naegeli. (C). Widely dis- 

 tributed; microcenobial colonies were commonly 



found in September. 

 Cosmarium crenatum Ralfs. (T). Shallow water. 

 Cosmarium cyclicum Lundell. (R). Western end of 



lake. 

 Cosmarium pygmaeum Arch. (R). 

 Cosmarium quadrum Lund . (R). 

 Cosmarium reniforme (Ralfs) Archer. (R) 

 Crucigenia irregularis Wille. (A). Surface during 



August. 

 Crucigenia rectangularis (Naegeli) Gay. (R). 

 Dictyosphaerium ehrenbergianum Naegeli. (R). 

 Dictyosphaerium pulchellum Woods. (A). Widespread, 



especially in spring and autumn. 

 Eudorina elegans Ehrenberg. (C). Shallow water, 



particularly in August and September. Maximum 



abundance was estimated at about 300 colonies 



per liter, 

 Elaktothrix gelatinosa Wille. (R) 

 Elaktothrix viridis (Snow) Printz. (R). 

 Geminella sp. (R). Shallow western area. 

 Gloeocyst is gigas (Kiitzing) Lagerheim. (R). 

 Gonatozygon monotaenium DeBary. (T). 



124 



