376 
waters rise in proportion. The readjustment which this ne- 
cessitates so modifies production that its movement differs, 
though the difference is slight and consequently the less sig- 
nificant. 
On Aug. 15 and 29 we deal again with a phenomenon simi- 
lar to that of May 21, namely, a pulse of large production in 
Dogfish Lake with an accompanying one of lesser amplitude 
in Quiver. The pulse in Dogfish was again later, apparently, 
in reaching its culmination (on the 15th) than that in Quiver 
(on the 7th), and its decline (93 per cent.) on the 22d more 
complete than that which Quiver attains (63 per cent.) on that 
date from its maximum (4.36) on the 7th. The conditions in 
Quiver Lake are further complicated by the fact that on the 
15th river water was just beginning a temporary invasion at 
the point of collection (see hydrograph, Pl. XXXI.). Save for 
this invasion the similarity of movement might perhaps have 
been preserved on the 15th. The abrupt and extreme decline 
in Dogfish Lake on the 22d, however, with the resulting inter- 
ruption of the similarity of movement on the 29th, is in some 
way related to the excessive development of the 15th, which 
may bring into operation again the factors above suggested in 
connection with the ike phenomenon in May. It seems not 
improbable that the sharper localization in Dogfish Lake due 
to absence of current and tributary waters and the presence of 
these factors in Quiver tends to intensify environmental in- 
fluences or inherent tendencies of the plankton in the one area, 
and to minimize some if not all of them in the other, and that 
this differentiating influence of these purely local factors is - 
fundamentally the cause of the dislocations and disturbances 
of the otherwise similar movement in production in the two 
lakes. These exceptions seem, however, to emphasize the es- 
sential similarity in the production in the two areas, a similar- 
ity founded on the common factors of the environment, shared 
equally by both, and on the identity, in the main, of the con- 
stituent organisms of the plankton. 
The general hydrographic conditions of this year affect 
