
¥ 
213, 
September. Apstein (’96) finds that this species (including S. 
tremula and S. grandis) is one of the most abundant in lakes near 
Pl6n, with variable maxima in different bodies of water. He finds 
it perennial in one case, and reports vernal maxima. Winter eggs 
were found in March and April. 
Syncheta stylata Wierz.—Average number of individuals, 120,391 ; 
oi eggs, 17,/97. In 1897, 42,577 and 9,127; in 1896, 24,099 and 
pe>- im 1895, 155,880 and 2,418; in 1894, 8,582 and 132. This 
species affords an exception to the general rule hitherto observed 
among the rotifers of our plankton in that it is more abundant in 
1898 than in the previous year. As will be seen in the following 
table both the vernal and autumnal pulses are unusually large in 
1898, while in the previous year the vernal pulse is only moderate 
and the autumnal pulse is scarcely to be detected. For some 
reason the prolonged low water and sewage contamination of the 
autumn of 1897 was not favorable to the usual growth of this 
species. It may be that it was crowded out by the unusual develop- 
ment of Polyarthra at that season (Pl. V.). 
PULSES OF SYNCHATA STYLATA. 





















Year Date Temp. No. Date Temp. No. Date | Temp. | No. 
on = Ee ee ees 
a ee 
1896 | Jan. 6 ae | 9 Heese | eee) ee | ee Se 
es Soe 3,648 
a) — || | |) ——— | —— 
1898 Jane 25 SyHe LOS || =< — ——— || “Mars Bee 6,400 
eee 2: byl 58,000 
1899 Jan. 14 34° 12,000 | Feb. 14 320 19,200 | Mar. 21 Sih 5,600 
; Year Date Temp. No. Date Temp.| No. Date Temp. | No. 
1894 ——— —_ — 
1895 Apr. 29 64° 219,123 
1896 Apr. 29 70° 380,586 May 25 58 10,800 | June 17 76° 79,200 
1897 May 25 66° 643,680 
Wales) | == — | May 3 60° /1,139,000 | June 21 TN 1955200 
set 70° | ’ 61,600 | | 









