332 SCOTT’S LAST EXPEDITION 
waters which had fallen to the bottom. These samples were ob- 
tained by letting down a weighted tube on the end of the sound- 
ing 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. 
When trawling in McMurdo Sound it was a common occur- 
rence to find that nearly half the catch consisted of dead animals. 
From an examination of the summer temperatures at vari- 
ous depths in several parts of the Ross Sea it was found that a 
temperature of + 1-0° Centigrade was hardly ever reached. 
The usual temperature was slightly below 0° Centigrade. 
At these low temperatures bacterial decomposition is at a 
minimum, and the food supply of the ocean remains in cold stor- 
age. However, a small amount of decomposition must take 
place to allow of the production of nitrates for the plants. 
The abundance of plankton in Antarctic waters is shown by 
a brownish discolouration of the sea produced by the diatoms. 
Another indication is given by large numbers of whalebone 
whales, which feed upon the plankton. 
It is true that only about three species of whalebone whales 
were recognised south of the pack, but the number of individuals 
seen daily around the ship was very great. The two commonest 
species seen were Balenoptera Sibbaldi, the Blue Whale, and 
Balenoptera rostrata, the Pike Whale. 
The large schools of killer whales, Orca gladiator, are an 
indirect indication of a plenteous food supply, because they feed 
upon seals and penguins, which in their turn live upon the 
plankton. 
If it was fully realised by whalers that there is a natural 
reason for the abundance of whales in the cold waters of the 
polar regions, they would not exploit warm seas such as that off 
the north of New Zealand with a ‘trying out’ plant suitable for 
South Georgia or the South Shetlands and so lose large sums of 
money. 
