fig 
striking instance of marked inequalities in distribution within 
small areas, of at least one plankton organism. 
Carteria showed great variation in the amount of chlorophyll 
present. Some individuals were practically colorless. It seems 
very probable that in the presence of great abundance of partially 
decayed organic matter such as occurs ina sewage-laden stream, 
Carterta may become largely holozoic in its nutrition, as Zumstein 
(99) has shown to be the case with Euglena. The literature of 
fresh-water plankton contains no record of a similar preponderance 
of Carteria in other localities, though its occurrence has been occa- 
sionally noted in the plankton. 
The chemical conditions under which this great pulse of Carteria 
appeared in the autumn of 1897 can be followed in Part I., Plate 
XLIV and Table X. The high chlorine and the great increase in free 
ammonia and nitrites indicate the decay of sewage; the high 
nitrates and albuminoid ammonia show that there was no lack of 
some at least of the important sources of food. The two principal 
pulses appear September 7 (2,846,250,000) and October 5 (6,476,- 
400,000), with a minimum of 680,400,000, on September 21, sep- 
arating them. Both of these pulses are attended by sharp declines 
in nitrates and nitrites and free ammonia, and very slight decreases 
in organic nitrogen and albuminoid ammonia. Either the first 
three substances named or those matters which supply them by 
their decay, are thus noticeably utilized at the times of these pulses. 
The relation of the Carteria to the volumetric pulses is (Pt. I., 
Pl. XI.) not a constant one. The Carteria pulse of September 7 
lies in a slight depression between two maxima of the volumetric 
curve,and a week prior to the autumnal culmination on September 
14 at 19.8 cm.? per m.*. It thus appears during the growth period 
of this volumetric maximum. The second and larger pulse of 
Carteria, on October 5, coincides with the second volumetric max1- 
mum, and in fact fluctuates throughout with it. Though Carteria 
constitutes but a small part of the actual catch of the silk net, 
owing to leakage through the silk, it is apparently an important 
factor in the food cycle which builds up such maxima. 
Ceratium brevicorne Hempel.—This species appeared in small 
numbers in isolated instances from April through October. It 
varies towards C. hirundinella, but the small numbers in which it 
has occurred have not as yet afforded sufficient ground for regard- 
