214 













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 perennial in 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 
~ exceed 2,500. The optimum conditions for the species in our 
-. waters are 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 SYNCHETA PECTINATA. 



Year Date Temp. No. Date Temp. ‘No. Date Temp. No. 







1896 Mar. 3 3D 6,360 Apr. 10 46° DUBE CNR) | —= | oS 









1898 ——_ = |S eS ZO iif 1,600 | June 21 io | 1125000 



Year Date Temp. No. Date Temp. No. Date Temp. No. 






1894 July 13 83° 74,606 



1895 July 23 go° 1,749 | Aug.12 | 85° 175,230 | Sept. 12 | 79° |. 27,740 
1896 July 10 go° | 22,200 | Aug.26 | 75° oe40g —— 
: MPS 82° | 38,000 
1897 — Aug. 10 | 81° 5382008 
at2a e780 9\|-964 000 
1898 July 19 | 84° | 20,800 | Aug. 2 78° 12,000 | Sept. 27 | 73° | 30,400 
eG ee WO 3,200 

1898 Deen a) 2,500 











