cted, the castings, the food dragged into the burrows. Pour
water into the jar and observe the actions of the worms. Can an
earthworm live in water?

Place an earthworm on a moist plate or board and direct the pupils to
study it, as follows:

Distinguish the head from the rear end, the upper from the lower
surface. Observe the means of living. To assist in the latter
observation, stroke the worm from rear to head and find the four double
rows of bristles. Why is it difficult to pull an earthworm out of its
burrow?

Find the mouth. Has the earthworm any eyes, ears, or nose? Place a pin
in the path of a moving worm and try to explain why it turns aside
before touching the obstacle. Test the sensitiveness to feeling. Why is
it cruel to put an earthworm on a fishhook?

From the soil castings found in the jar, infer the value of earthworms
for enriching and pulverizing soil. (See "Soil Studies", p. 269.)

REFERENCES

Bailey and Coleman: _First Course in Biology._ Macmillan Co. $1.25.

Crawford: _Guide to Nature Study._ The Copp, Clark Co. 90 cents.

Kellogg: _Elementary Zoology._ Holt & Co. $1.35.

THE AQUARIUM

A large glass aquarium may be purchased from any School Supply Company
at a cost of a few dollars, but a small globe-shaped aquarium such as is
used for gold-fishes will be found suitable for school purposes. If it
is not possible to secure either of these, a large glass jar, such as a
battery jar or large fruit jar, will be found to answer quite well.

To set up the aquarium, put into the jar about two inches of clean shore
sand (sand from a sand pit, washed until the water comes away clear,
will do). Secure from a pond some water-plants, place these in the jar
with their roots covered with sand and secured in position by small
stones. Pour in water until the jar is nearly full, taking care not to
wash the roots out of place, and then put in a freshwater clam and a few
water snails. These are scavengers, for the clam feeds upon organisms
that float in the water, while the snails eat the green scum that grows
on the glass.

The other aquarium specimens may now be put in. One fish about three
inches long to a gallon of water is about the right proportion. When
there is a sufficient quantity of plant life to keep the water properly
oxygenated and enough animal life to supply the carbon dioxide necessary
to keep the plants growing well, the aquarium is said to be _balanced_.

The balanced aquarium does