291 



of the paper will, I believe, find that in the main the conclu- 

 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., PI. 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 cm.^ respectively. The maximum catch, 10.18 cm.^per 

 m.^ (plankton, 9.67; silt, .51) was taken Aug. 15, and the min- 

 imum, .25 cm.^ (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, to a 

 minimum in October-December. 



A comparison of the record of 1894 (PL VIII. ) with that of 

 other years (PI. IX. -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 was a 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, 



