Zid 
numbers of that year, while the larger numbers in 1897 may be 
attributed to the more stable conditions. The small numbers in 
1898 do not seem to be correlated with any feature of the environ- 
ment. 
This species has been found in every month of the year, and is 
thus perennialin our plankton. As will be seen, however, in Table I., 
the most of the occurrences and a much greater proportion of the 
individuals are found between May and October, and thus above 
60°. The same limitations are found in the other years, with the 
exception that in 1896 there was a more continuous and larger de- 
velopment from the last of February. In the table which follows 
it may be noted that all of the pulses but four are at temperatures 
above 70°, and of these four none exceeds 25,000, and two do not 
exeecd 2500. The optimum conditions for the species in’ our 
waters aré therefore above 70°. The average temperature at the 
time of the larger pulses is near 80°. The vernal pulses are poorly 
defined, as are likewise the autumnal ones. It is a midsummer 
species in our waters, with its maximum in August. 
PULSES OF SYNCHZTA PECTINATA. 
Year Date Gres No. Date Temp. No. Date Temp. No. 
1894 | ——— | —— —— | —— | —| — 
1895 | ———- | —— | —— | ——— | ——}| ——J| ——— | ——] —— 
1896 | Mar. 3 35° BiccovolAoest00 | 46° 24,436 | ——— | ——| ——— 
1897 — | —— —— 
1898 ————— —_ | ——- Apr. 26 Bye 1,600 | June 21 77° | 112,000 
Year Date Temp. No. Date Temp. No. Date Temp. No. 
1894 July 13 83° 74,606 aa 
1895 July 23 80° 1,749 Aug. 12 85° 175,230 | Sept. 12 79° 27,740 
1896 July 10 80° 22,200 Aug. 26 132 50,400 | 
= 23 82° 38,000 
1897 = SS SS Aug. 10 caylee 83,200 
er 78° 264,000 
1898 July 19 84° 20,800 Aug. 2 78° 12,000 | Sept. 27 W32 30, 400 
sor ao 82° 3,200 
1898 Dec. 13 330. 2,500 
