332 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIE'Y. 
encroachments may be great or small, may be confined to 
certain periods of the year, or may. be continuous so as to 
reduce the original curve more or less along its whole 
length. Finally, the lines CC and DD may indicate 
‘weather’ conditions 
the manner in which unusual 
(under which we include changes in salinity and tempera- 
ture of the water as well as any unusual currents, storms, 
sunshine, &c. may retard (as at C in spring) or prolong 
(as at D in late autumn) the normal increase in the 
population. 
The resulting curve due to the combination of all 
these factors in this supposed case would then be as shown 
in fig. 16, Il. Whether it may eventually be possible from 
a consideration of all the environmental conditions, and 
the comparison of different years, and different localities, 
to disengage from one another the action of these three 
factors, so as to be able to predict what the effect of 
weather (in the widest sense) may be upon the normal 
plankton supphes and upon the Fisheries of any sea-area 
is quite another question, and one which without much 
further experiment and comparison of results under 
varying conditions cannot yet receive any definite answer. 
But the problem does not seem so complicated as to forbid 
all hope of ultimate analysis and solution, and conse- 
quently it seems desirable that the work should be 
vigorously prosecuted in as many localities as possible, 
not as an aimless collection of statistics, but asa definite 
experimental research. 
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