Mv 
tackle the problem which ought to be tackled. What we 
should aim at ascertaining is not what a fisherma 
catches, but what there is for him to catch. We must in 
fact get series of accurate observations which will give 
us fair samples of the more sedentary populations of our 
seas on the different grounds, such as trawling grounds, 
shrimping grounds, nurseries and spawning banks, at the 
different seasons. I have spoken of this in brief as 
to aim at taking an approximate “census”’ of the sea, 
but that, of course, is too ambitious a word, and indicates 
an exactness to which we probably could never hope to 
attain. Still the word serves to remind us of our 
approximate aim, and if we can even determine the 
numbers of a species on an area between wide limits, it 
will be of great importance. 
The investigation is, of course, beset with difficulties, 
but they are not insuperable. One great difficulty is to 
determine to what extent we can safely draw conclusions 
from our observations. In speaking of this matter 
recently to a Liverpool audience I made use of a homely 
illustration, which may be worth repeating here as a 
possible help to some readers in realising the problem. I 
compared the investigation to the case of an aeronaut in a 
balloon trawling along the streets of Liverpool through a 
thick fog. We may suppose that a drag in the neighbour- 
hood of University College would yield some students— 
male and female—and a professor; one somewhere about 
the docks would doubtless capture some sailors, dock 
labourers, and a stevedore or two, while a lucky shot 
opposite the Town Hall might bring up a policeman, an 
electric car, and a couple of Aldermen. Now, if such 
experiences were repeated over and over again, would the 
conclusions that might naturally be drawn by the intelli- 
gent aeronaut as to the relations between organisms and 
B 
