423 



greatest in the most differentiated localities, Quiver and Dog- 

 fish lakes. It might also have been expected in Flag Lake (PI. 

 XXXI V.) if examination had continued there beyond the mid- 

 dle of July. It would seem, accordingly, that similarity in the 

 course of plankton production in different localities is to a 

 large extent a function of the community of environmental 

 factors, and possibly also of the similarity of the constituent 

 organisms. 



1898. 



(Table IX., PI. XLII.) 



There are 22 collections in this year, at fortnightly inter- 

 vals, in March-December. The average production for the year 

 is the unsurpassed amount of 44.08 cm.^ per m.^ with a maxi- 

 mum, also unsurpassed in our records, of 224.48 on Aug. 23. An 

 unusually high level of production is also maintained from Aug. 

 9 to Dec. 13, averaging 63.54 cm.^ and falling below 30 in but 

 two instances. 



Water re-entered Phelps Lake with the flood of February, 

 river stages passing 8 ft. on the 12th and 10 ft. on the 20th. 

 From this latter date until June 28, w^ith the exception of 4 

 days in May, levels continued above 10 ft., so that a continued 

 current of overflow from the bottom-lands to the north passed 

 through the lake to the river. Declining river stages continued 

 from June 28, passing 8 ft. July 9, thus permitting a run-off for 

 a total of 138 days from the lake to the river in the period of 

 spring and summer floods. To this must be added 7 days of de- 

 clining levels above 8 ft. in the November-December rise, mak- 

 ing a total of 145 days of contributions to channel w^aters from 

 this lake. This is the most extended period of contribution in 

 the years of our operations, and is a result of the unusually 

 high and prolonged floods which brought the average height of 

 the river up to 8.02 ft., almost bank height, for the year. 



The plankton content of Phelps Lake waters in the 10 col- 

 lections made during the period of discharge above noted, is in 

 excess of that in the channel in 7 instances by from 1,4- to 15- fold 



