Io ANIMAL ACTIVITIES. 
In this way the water siphons over into the sink. To 
prevent the passage of insects through the siphon, attach 
Fic. 10.—Other Pondweeds. 
growing fresh-water plants, an 
it to a_ tunnel 
having the open- 
ing covered with 
wire gauze. 
Hydra. Collect 
small sticks and 
dead leaves, with 
some mud and 
water, froma fresh- 
water pond, or from 
ditches used for 
draining swampy 
places. Place 
these in glass with 
d renew from time to 
Fic, 11.—The Hydra (magnified). 
time the water lost by evaporation. Collect from 
several localities in separate jars, and label the jars 
