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; 
of eggs, 17,797. In 1897, 42,577 and 9,127; in 1896, 24,099 and 
Sl tnt 895. 155,880 and 2,413; im 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 (PI. V.). 
PULSES OF SYNCHATA STYLATA. 
Year Date Temp. No. Date Temp. No. Date Temp. No. 
1894 ae eee See | Se ee | ee 
1895 a ee ee ee cy 
1896 Jan. 6 32° 13,356 —_— 
ae ZO Soe 3,648 
1897 == === ——= == 
1898 Jan. 25 S20 BRS) | —————= =— = || Were, 33° 6,400 
ae 22 Bile 58,000 
1899 Jan. 14 34° 12,000 | Feb. 14 gue 19,200 | Mar. 21 Sie 5,600 
Year Date Temp. No. Date Temp. No. Date Temp. | No. 
1894 oe 
1895 Apr. 29 64° 219,123 
1896 Apr. 29 70° 380,586 | May 25 Sy 10,800 | June 17 76° 79,200 
1897 ed a —<—— || Wiles 2S 66° Oytst (otsk0) || $= a th rare oe 
May 2) fe 609 39,0001) jane 21 |) °77°)| 795,200 
CE sii 70° 61,600 
