The available data indicates that Diaptomus had two periods 

 of abundance, one in late May, the other in early July. During the 

 period May lh-19, the mean for the area was 6 per liter. The number 

 increased rapidly in the next few days to 12 per liter. During June 

 the count decreased to h per liter, but in early July increased to l8. 

 Thereafter (with the possible exception of the two periods for which 

 no data are available) the counts were low, and in November, Diaptomus 

 was present only in traces. 



The seasonal distribution of Cyclops was similar to that of 

 Diaptomus. It had two periods of abundance and these coincided with 

 those of Diaptomus. In the early period of abundance, Cyclops was 

 the more numerous; in the second Diaptomus was more numerous. The 

 mean number for the season was the same for both (6 per liter) , 



Daphnia also had two periods of abundance. The first came in 

 the period following the first period of abundance for Diaptomus and 

 Cyclops, but the second period of abundance came at the same time for 

 all three genera. At times Daphnia was more abundant than either of 

 the others, but never more abundant than the two combined. Thus the 

 plankton was dominated by copepods. During and after late September, 

 Daphnia vias very rare. 



Diaphanosoma was a consistent member of the plankton, but 

 never became very abundant. It appeared in largest numbers (U per liter) 

 in late July, During most of the season there was less than 1 per 

 liter. Epischura and Limnocalanus appeared only occasionally. In 

 a few samples Epischura had a count in excess of 1 per liter, but 

 the mean for the section was always low. Another rare form was 

 Bosmina; it disappeared during late July and early August and never 

 had a mean count of more than 1 per liter. Leptodora was even more 

 rare than Bosmina; during h of the 12 periods no specimens were taken. 



It is clear from this brief discussion th.-t the bulk of the 

 plankton Crustacea was contributed by three members, Diaptomus, 

 Cyclops, and Daphnia. Diaphanosoma and Bosmina were present most of 

 the time but never in large numbers. Epischura, Limnocalanus, and 

 Leptodora were present occasionally in small numbers. It was dis- 

 tinctly a copepod plankton. It is worthy of note that all of the 

 Crustacea were rare in the month of Noven:ber. Data for this month 

 were not obtained in I929 and 1930, 



Season nf I929 



In 1929 plankton studies were begun May 20 and discontinued 

 October 22. All samples were taken with the plankton trap. Samples 

 were taken from the following stations: I8, 37A, 59A, 82, 8F, 158^ 

 68, and 75. The location of these stations may be seen in Fig. 1, 

 The results are given in Table 69, which is made up on the same plan 

 as Table 68. The data on Diaptomus, Cyclops, Daphnia, and nauplii 

 are shown graphically in Fig, 19, 



21$ 



