hing tubes in the aphis or green
fly. The spiracles or pores are marked O, the breathing tubes T.

Some insects which live in water, such as the water-beetle, breathe air
in the same way as their relatives who live on land. To do this they
have to come frequently to the surface of the water to take in fresh
supplies of air. In the great Dyticus water-beetle this is done in a
curious way. The creature, rising to the surface, first thrusts its tail
up into the air, and then bending it downwards, lets the air rush in to
fill the space between the body and the upper wing-cases. This done, the
tail is pressed back again, and the beetle returns to the depths, where
the imprisoned air is taken in through the pores into the tubes.

Besides the system of tubes just described, many insects possess a
wonderful system of air-cells, which give extra help in breathing during
flight. These air-cells are largest in insects which fly most. It is a
curious fact that birds have an exactly similar system; in many cases,
even the bones of birds are filled with air. It is generally stated,
indeed, that birds with the strongest flight have the most 'pneumatic'
bones. This not quite true, for the swallow, for example, has the long
bones of its wing filled with marrow, and not with air. Other birds,
however, like the storks, which fly much, and the owls and nightjars,
have all the bones in the body thus filled with air which they obtain
from the air-cells.

W. P. PYCRAFT, F.Z.S., A.L.S.

AFLOAT ON THE DOGGER BANK.

A Story of Adventure on the North Sea and in China.

(_Continued from page 227._)

CHAPTER V.

'I shall not be able to make plum duff,' said Charlie to Ping Wang,
about half an hour after his loss of the cook's recipe-book.

'There will be a row if the men discover that you don't know how to make
it,' Ping Wang declared, looking serious. 'But never mind that, I have
something more important to tell you. Come aft; the skipper may be
listening to what we are saying.'

They went right to the stem of the trawler and stood against the
gunwale.

'No one can come near us without our seeing him,' Ping Wang said, and
continued at once: 'Could you swim a mile in a sea like this?'

'I think so.'

'Then let us desert the _Sparrow-hawk_ when darkness comes on.'

'But where are we to swim to? I don't see any boats within five miles of
us.'

Ping Wang pointed to the horizon, where the smoke of about half-a-dozen
trawlers