291 
of the paper will, I believe, find that in the main the conelu- 
sions arrived at rest on a body of confirmatory data so large as 
to counterbalance to some extent the probability of vitiating 
error from this source. The distribution of the error is, more- 
over, continuous throughout the whole series of data, with, 
however, some probability of variation with the stability of the 
hydrographic conditions. Finally, the conclusions to be drawn 
in subsequent pages rest upon data which to a large extent 
rise above the level of the error resulting from the irregularity 
of distribution. 
PLANKTON PRODUCTION. 
1894 
(Table III., Pl. VIII.) 
Ten collections were made by the oblique-haul method in 
this year between June 12 and December 15. The volumes of 
plankton, silt, and total catch per cubic meter average 2.49, .28, 
and 2.77 em.’ respectively. The maximum catch, 10.18 cm.* per 
m.* (plankton, 9.67; silt, .51) was taken Aug. 15,and the min- 
imum, .25 em.’ (plankton, .10; silt, .15), on Nov. 11. The series of 
ten catches form a somewhat regular curve, rising during July 
and August, and declining, most rapidly in September, toa 
minimum in October-December. 
A comparison of the record of 1894 (Pl. VIII.) with that of 
other years (Pl. [X.-XII.). as shown in the accompanying table 
of averages (p. 292), and with the conditions of temperature and 
hydrograph, will serve to throw light on the significance of the 
plankton volumes of this first year of our collections. 
As shown on pages 168 and 164, this wasa year of normally 
located high and low water, with March, May, and September 
rises all so reduced as almost to eliminate overflow stages and 
to prolong low-water stages, resulting in the low average height 
of 4.63 ft. above low water. Our collections all fall in the sta- 
ble period, broken only by the September rise. They therefore 
afford no data on the spring maximum of plankton production, 
