THE PLANKTON 329 
pound honey jar, while another requires two seven-pound fruit 
jars to contain it. 
The size of a catch, of course, depends upon various factors, 
such as the size of the net, the time it was fishing, or the amount 
of water passing through it, and the quantity of plankton in the 
sea at the place where the haul was obtained. 
A small number of sea-water samples were collected from 
various depths by means of the Nansen-Pattersson water-bottle. 
These were generally taken from the areas in which plankton 
samples were obtained. The object of these water samples is to 
ascertain the salinity of the sea at different points and at differ- 
ent depths. 
Any change in the salinity means a marked change in the 
character of the plankton. 
The plankton catches, when sorted, will doubtless be found 
to contain many new genera and species to add to the list of the 
known forms of living things. The vertical hauls, which were 
generally made for quantitative purposes, will help to increase 
our knowledge of the relative abundance of the plankton over 
the oceans of the world and at different seasons of the year. 
Isolated observations such as these may be of small value in 
themselves, but every expedition which collects such data thereby 
adds its quota to the gradually accumulating mass of evidence 
and brings the time for generalisation nearer to hand. A knowl- 
edge of the relative abundance of the food supply of the ocean 
is not only of scientific interest but of commercial importance. 
On the homeward voyage two satisfactory hauls with the 
trawl were obtained, one off the Falkland Islands in a depth of 
125 fathoms, and the other off Rio de Janeiro in 40 fathoms. 
The trawl scrapes the bottom of the sea, and brings up a fair 
sample of whatever animals and plants it can entrap or uproot. 
So little scientific trawling has been done in the Southern 
Hemisphere that almost every haul has a chance of containing 
some creature hitherto unknown from the area in which the catch 
was obtained. | 
Animals which live at the bottom of the sea are known to 
zoologists as the benthos. 
During the outward voyage a day was spent on the island of 
South Trinidad by several members of the Expedition, and col- 
