14'2 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



tackle tlie problem which ought to be tackled. What we 

 should aim at ascertaining is not what a fisherman 

 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. Xow, 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 



