483 
impossible. That the reduction in light due to clouds does in 
a measure affect production might be inferred from the August 
—October records in 1896 and 1898. In the two years named, 
cloudy days and production in August are 2 and 8, and 1.12 and 
.91 cm.’ per m.’ respectively ; in September they are 11 and 2, 
and .38 and .69; and in October 3 and 16, and 1.11 and .24. Hy- 
drographic conditions are not remarkably different in the two 
years, and while their differences in this respect are doubtless 
potent, causing differences in production, it still seems prob- 
able that the fluctuations in light are also operative. In any 
event in these three months the mean production runs higher 
in the year of fewer cloudy days and lower in the year of less 
sunshine, Similar relations will be found to exist generally 
in the production of the backwaters for these months (see 
table following p. 342). The statistical data of the synthetic 
organisms to be discussed in Part II. of this paper still further 
serve to demonstrate the correlation of light and plankton pro- 
duction. The necessity of light for the process of photosynthe- 
sis on the part of the phytoplankton places this factor at the 
very beginning of the chain of relations whose later links are 
the larger animals of the zodplankton which constitute the 
greater proportion of the volume of the catch of the silk net— 
the basis of the present discussion. 
VEGETATION AND PLANKTON PRODUCTION, 
It is evident that our investigations afford a unique oppor- 
tunity of determining the effect of vegetation (the word being 
here used to refer to the coarser aquatic growth as distin- 
guished from the microscopic phytoplankton) upon the course 
of plankton production with reference to both its volume and 
constitution. 
The conclusions to be drawn from our observations with 
reference to volumetric production, already suggested in the 
detailed discussion of production, will be summarized and dis- 
cussed here, though some of the data upon which they rest lie 
outside the scope of the present paper. 
