175 
Cytology of Polyphagus Euglenae. 
encysted condition, but on placing them in a saucer of tap-water they 
soon became motile, and remained in this condition for several days. 
They then passed into a resting stage again, becoming rounded off and 
surrounded by a thin membrane, and formed a scum at the surface of the 
water. The Fungus then appeared and developed very rapidly. 
Massee (’91) says that it is rare, but it has frequently appeared in my 
cultures of Euglena from various sources, and I suspect that it is to be 
found very commonly in cultures of Euglena from sewage filter beds. 
It does not appear so readily on cultures of Euglena obtained from farm- 
yards, but if, as suggested by Kwakine (’86), the cultures are started 
in a dilute solution of albumen in water, the parasite usually makes its 
appearance. Its presence is indicated by a greyish appearance of the 
green scum, and, when it occurs in quantity, by a peculiar roughness on 
its surface which is very characteristic, and quite different from that 
brought about by other parasites, of which a considerable number, including 
many of the Chytridiaceae, occur frequently on Euglena. 
The parasite spreads very rapidly. A single cell, with its numerous 
branching pseudopodia or haustoria, may attack a very large number of 
individual Euglenae, frequently from thirty to fifty, or possibly even more, 
and in the early stages of development large sporangia with enormous 
numbers of zoospores are produced, by means of which the infected area is 
rapidly extended in all directions. In the course of about six days the 
colour of the culture changes from greyish green to yellow, and finally, 
when the Euglenae have been completely or almost completely destroyed 
by it, the culture becomes dark brown. At this stage the formation of 
zoosporangia has ceased and large numbers of zygotes in various stages of 
development will be found. 
Effect on Euglena. 
The Euglenae are only attacked by the parasite when they are in 
a rounded-off and encysted state. So long as they are motile, the haustoria 
are unable to obtain an entry. 
The haustorium quickly penetrates the Euglena cell by perforating the 
cell-wall. It then branches in all directions and soon brings about a com- 
plete disintegration of the cell contents. The first effect visible in the cell 
is that the chlorophyll bodies turn yellow or yellowish green. They then 
gradually disappear and in their place are found rusty red granules or 
masses of granules. The protoplasm at the same time becomes absorbed. 
Then the paramylum grains become broken up and the granules of the eye- 
spot separate from one another. The nucleus and the cell membrane at 
this stage are still to be seen, but the nucleus is gradually absorbed, and 
after a long time (several days) the cell-wall also disappears, and the rusty 
red granules become disseminated in the surrounding liquid. 
