ENGLENA VIRIDIS (EHRENBERG.) 151 
Dileptus, Amoeba, etc. Numerous Rotifera, too, together with the 
protozoa, decrease the cultures by feeding on the Euglena cells. 
Protozoa as well as bacteria were rife in the organic nutrients but not 
in the inorganic nutrients nor in the creek water and tap water. 
* While the encysted cells are still alive, the water mould, Polyphagus 
Euglenae grows rapidly in the cultures, especially so in the unfiltered 
creek water. The growth and decline of this mould are an index 
on the condition of the encysted Euglena cells. Thus, it declines in 
the cultures in the darkness sooner than in the light. It was ob- 
_served that, like some of the other water moulds such as Saprolegnia, 
the zoospores of Polyphagus Euglenae swarm only in the morning. 
1 
Reproduction 
Reproduction in the successful cultures begins about the second 
or the third day and, at first, there is only longitudinal division, the 
parent cells coming to rest at night, and the daughter cells separating 
in the morning. As the cultures (in light) advance, many of the » 
cells encyst and there arises from each encystment, four, eight, and 
even sixteen cells; four being the most common number. There are 
many eight-celled encystments but relatively few sixteen-celled 
groups. 
Summary 
1. The discharge of oxygen gas from masses of Euglena cells in 
the sunlight indicates the process of photosynthesis. 
2. The green plastids of Euglena viridis are chlorophyll-bearing. 
3. Euglena viridis does not thrive in the dark and it, therefore, 
must depend, at least very largely, upon photosynthesis for its nutri- 
tion. There is an indication, however, that Euglena viridis does make 
use of organic nutrients to a very slight degree, in the fact that it 
seems to be a little more successful in such media when in the dark 
than in inorganic nutrients. This may be accounted for in part, 
however, by the fact that the protozoa and other enemies of Euglena 
are less dependent upon it in organic media than they are in the 
inorganic media. 
4. Reproduction in Euglena viridis, as observed in this study, is 
by longitudinal fission of resting cells, and by the division of encysted 
cells into four, eight, or even sixteen cells. 
Saint Clara College, 
Sinsinawa, Wisconsin. 
