48o SCOTT'S LAST EXPEDITION 
These comprise 27 collected during the first year, 48 the 
second year, and 60 the third year. 
Also 96 samples of sea-water were obtained. 
The increase in the relative size of the plankton catches 
as we left the warm seas around New Zealand and entered 
the cold waters of the far south was very marked. This 
increase was especially noticeable in the case of the 
diatoms. These minute plants became so numerous as to 
choke the meshes of the net after it had been fishing only 
five minutes. In the middle of pack ice the diatoms were 
much less numerous. This may have been due to the ice 
floes shutting out the sunlight or to an alteration in the 
salinity of the sea caused by the melting of the ice. 
Some fifty samples of the muds and oozes from the 
bottom of the sea between New Zealand and the Antarctic 
were collected. A rough examination of some of these 
showed them to consist of the skeletons of diatoms and 
other inhabitants of the surface waters which had fallen to 
the bottom. These samples were obtained by letting down 
a weighted tube on the end of the sounding wire. The 
tube would sink vertically into the mud and bring up 
several inches of the deposit. Thus, if there were six 
inches of mud in the tube a sample taken from the bottom 
of the tube would come from about six inches below the 
surface of the sea floor. 
In the Ross Sea it was found that many of the diatoms 
in a sample of mud taken from four inches below the 
surface of the deposit still contained their protoplasm 
and chlorophyll bodies. In other words, they were 
undecomposed. 
