CHAPTER XII. 
THE HYDRA AND SOME CC@ELENTERATES WHICH 
LIVE IN COLONIES. 
Fresh-water Hydra. In warm weather hydra may 
be found near the surface of fresh water on leaves or 
sticks or attached to the stems of aquatic plants. If 
such leaves or plants be collected and placed in a plate, 
or jar of water in the sunlight, hydra may be seen in a 
short time. As soon as they have been found, transfer 
them with the plants on which they feed to an aquarium, 
where they may be easily kept all winter. They feed 
on cyclops, daphnia, and other small crustaceans. 
These are commonly found in the same places as the 
hydra and probably will appear in the water with the 
leaves collected. If they do not appear keep on col- 
lecting dead leaves from different localities until they 
are found. Both hydra and its food may be found 
almost anywhere if patience and care be used in collect- 
ing. When wanted for use it is easy to transfer hydras 
to a watch-glass by removing them from the side of the 
aquarium with a knife and dipping them out with a 
glass tube. 
Note the appearance of hydras as you see them in 
the aquarium. 
What is their size? their shape? Do all have the 
same shape ? 
Look for branches and buds. How many do you 
find on any hydra? 
What is the color of hydra ? 
What movements can the hydra make ? 
128 
