782 THE AMERICAN NATURALIST. (VoL. XXXIX. 
2. Arcella and Difffugia will often be found in ordinary 
Ameeba cultures, or in cultures made with dead water-lily 
leaves. In rather fresh cultures, these Protozoa may be found 
creeping along the surface of the vegetation. Take up a mass 
of the Ceratophyllum between the fingers and bruise it briskly 
against a watch glass; add a /itt/e water to the residue that 
clings to the glass. It will usually contain Arcella and Dif- 
flugia. 
3. Chilomonas may appear at almost any time in Amoeba cul- 
tures ; but it is best to put up cultures especially for Chilomonas 
and Infusoria. Use Ceratophyllum and partly decayed water- 
lily leaves, and pack in bacteria dishes as for Amoeba, but use 
less plant material and more water. Cultures prepared in this 
way may mature in a very few days. Mount a drop of the 
water containing Chilomonas, together with a little of the slime 
or decaying vegetable material by means of which the specimens 
may be entangled. | 
4. Euglena will appear in some of the cultures put up for 
Amoeba, usually after the disappearance of Amoeba, four or five 
weeks from the date of starting the cultures, but occasionally it 
appears before Amceba. It makes a solid deep-green (not blue- 
green) mass at the edge of the dish, especially on the side to- 
wards the light. A thick, pale brown, feltlike and granular 
scum on the surface of the culture seems to be favorable to 
the presence of Euglena. Such a scum contains delicate fungi, 
diatoms, desmids, Arcella, etc. ' 
Euglena usually appears in only a few dishes, but in abundance, 
and lasts several days. Euglena is often associated with Phacus, 
which somewhat resembles it, but the latter organism is skate- 
shaped, and does not exhibit euglenoid movements. 
Keeping the cultures away from a strong light may prevent 
the formation of an excess of chlorophyll in Euglena. 
5. Paramacium — Prepare cultures in the same manner as 
for Chilomonas. Decaying water-lily leaves are especially good. 
The cultures require but a few days to mature, and last a long 
time. Mount a drop of water containing Paramoecia, together 
with a little of the decaying vegetable material about which they 
may collect. i 
