87 
out most of the summer, attending only approximately the sup- 
pressed and interrupted pulses of Melosira in that year of disturbed 
hydrograph. It has been recorded from the latter part of April 
till the middle of September, and, as a rule, above 60°. This beau- 
tiful little choanoflagellate is sessile upon the filaments of Melostra, 
principally upon the variety spinosa, and but rarely upon MW. varians 
or other planktonts such as Pediastrum. It is often associated 
with Bicoseca lacustris and is usually found upon the sides of the 
filaments, the bowl of the transparent brownish lorica being closely 
sessile upon the diatom. In one instance a lorica was found upon 
the corner at the end of the filament. The lorica had adapted 
itself to this novel situation by an angular indentation fitted upon 
the corner of the diatom. 
Syncrypta voluox Ehrbg.—Average number, 625. This species” 
has a definite and somewhat unusual seasonal distribution. In 
1898 it was found from March 1 to April 12, and reappeared Novem- 
ber 8, attaining a maximum of 13,500 on December 6, and of 43,000 
on January 1, declining then to 800 and rising on February 14 to 
4,800, and subsequently disappearing in the flood waters of March. 
It was not recorded 1n 1897. In1895 it appeared September 27 and 
continued for a month, reappearing in February and March, and 
not occurring after April 10. It has attained its largest develop- 
ment at minimum temperatures under the ice—43,000 January 3, 
1899, at 32.7°. The greater part of its occurrences in 1898-1899 
le very near this temperature, and but three in all the years lie 
above 50°. It is par excellence a winter planktont, or at least a 
cold-water one. 
Its occurrences in 1895-1896 lie near the beginning and the 
close of the seasonal pulse of Synura. In 1898-1899 the pulses of 
Syncrypta coincide in location with or immediately follow those of 
Synura. The resemblance of Synerypta to small colonies of 
Synura is striking, and this fact combined with the relation of their 
seasonal fluctuations raises the query if Syucrypta may not be an 
encysting stage of the Synura colony. Its life history should be 
fully worked out. 
Synura uvella Ehrbg.—Average number of colonies, 8,463. 
The seasonal distribution of this chrysomonad flagellate is some- 
What similar to that of its near relative Syncrypta. It is a 
perennial, though predominantly cold-water, planktont. It appears 
