262 Dar bishire. — On Actinococcus and Phy Hop kora. 
Fig. 7. Actinococcus roseus 
(Lyngb.) Kold. Rosenv. Vertical 
section of outer layers of nema- 
thecium : a. sterile outer cells of 
nemathecial filaments ; b. tetra- 
sporangia ; c. sterile inner cells, 
and d. the cells of the parasitic 
cushion. x 300 diam. 
Phyllophora also possess numerous 
pits, by means of which their cyto- 
plasm is continuous. Only on rare 
occasions is it possible to make out 
any connexion between the cells 
of the parasite and the host. In 
cases where the parasite has been 
growing in the host for some time, 
the filaments of the former often 
may grow a considerable distance 
down into the tissue of the thallus 
of Phyllophora in order to absorb 
more food-material for the cells 
of the tetrasporic fructification. 
The extramatrical filaments 
gradually form the nemathecium 
of the parasite. The outermost, 
radially disposed filaments grad- 
ually develop into tetrasporangia. 
Each cell of these usually un- 
branched fertile threads, gives rise 
to four tetraspores, with the 
exception of the two to four 
apical cells (Fig. 7). The inner 
and lower cells of the fertile 
filaments also remain sterile. The 
whole fertile nemathecial layer is 
in itself about 150-200 /ut deep. 
The sterile apical cells contain 
some clear, frothy cytoplasm and 
a distinct, though as a rule very 
much reduced, rhodoplastid. They 
are usually larger and longer than 
the tetrasporangia. 
The tetraspores are formed by 
cruciate division, the first cross- 
wall formed being placed at right 
