Jan, 1910.] 
Monochytrium, a New Genus. 
45 
in the usual way, sectioned 5-10/* thick, and stained on the slide 
with Heidenhein’s Iron Alum Haematoxylon and with Analin 
Safranin and Gentian Violet. Either stain is satisfactory but 
most of the drawings have been made from material stained with 
the Safranin- Violet combination. 
The youngest stages of the parasite found were imbedded in 
the cytoplasm of the host cell (Fig. 2). The}' were minute 
amoeboid cells whose size (3/x) corresponds rather closely with 
that of the segments of the zoosporangium. Not infrequently 
the perforations by which the young parasite had entered the 
host cell may be seen in section as thickenings on the inside of 
the wall of the host (Figs. 8, 10). In rare instances slight thick- 
enings may also be observed on the outside surface of the wall 
(Fig. 13). In other cells cut tangentially so as to allow one to 
look through the perforations (Fig. 3) one sees that the holes are 
surrounded by irregular cellulose thickenings. In appearance 
these collars resemble somewhat the irregular growths of bark 
around a healing wound on a tree trunk and suggest that they 
were secreted by the cytoplasm of the host cell in an attempt to 
repair the damage ; in many instances there are indications that 
such repair is completed for in most of the infected cells the 
points of entrance appear to be simply thickened places on the 
walls and no perforation can be observed by focusing up and 
down . 
In favorable locations the young amoebulae imbedded in the 
host cytoplasm are extremelv abundant, hardlv a cell being free 
from parasites (Fig. 1). Moreover, there are frequently nearly a 
dozen in a single cell (Fig. 2). Their minute size precludes very 
exact observations as to their structure but as compared with 
the segments of the zoosporangia from which they are supposed 
to have come their cytoplasm is less dense, containing, appar- 
ently almost from the beginning, several relativelv large vacuoles 
(Fig. 5), between the meshes of the reticulate cytoplasm. Of 
the nucleus little can be seen beyond the deeply staining nucleolus 
and the nuclear membrane, though by analog}' with the larger 
nuclei of later stages it may be supposed to have more or less of a 
chromatin reticulum in addition. Lying in the cytoplasm close 
beside the nucleus there is frequently a deeplv staining body 
(Figs. 5, 6) whose general appearance at once suggests a centro- 
some. No such structure was observed at any other stage of the 
life history but it is not impossible that one may be associated 
with the flagella of the zoospores. But as long as the zoospores 
themselves remain unknown it is idle to speculate on the matter. 
The deeply staining bodies in question occur, however, with suf- 
ficient frequency to make it very desirable to be able to offer some 
interpretation of their presence. 
