170 BACTERIA. FUNGI. 
processes of the parasite fungus pushes out of the cell-cavity of the invaded 
Spirogyra into the surrounding water again and there swells up into a spherical 
vesicle, within which the protoplasm divides into eight spores. These spores are 
then set free as swarm-spores and attack new healthy Spirogyra-cells. 
Materially different is the behaviour of the parasite Chytridiwm Ola, which 
attacks the green cells of fresh-water Gidogonize. Its roundish swarm-spores are 
furnished each with one long cilium, and swim, searching about in the water until 
they meet with an (Edogonium-cell to their taste just occupied in the formation of 
oospores. When they find one, they fasten upon it and send infinitesimally fine 
hair-like tubes (which have been called rhizoids) into the interior. By means of 
these tubes they derive their nutriment from the host. The body of the parasite, 
which remains outside the invaded cell, increases in size, and at length grows out 
into a sporangium; the latter opens at the top by a lid and once more sets free 
swarm-spores into the surrounding water. 
Polyphagus Euglene, a member of the Chytridez, is parasitic on the green 
cells of Euglene living in water. The swarm spores of this microscopic fungus 
(see fig. 334) are oval and furnished, like those of Chytridiwm Ola, with a long 
eilium. They swim about the water with the non-ciliate extremity leading, so that 
the cilium appears to be a tail at the posterior end. As soon as these swarm-spores 
have come to rest, they assume a spherical form and send out in all directions thin, 
hair-like tubes, which search for a host. When a tube reaches an Euglena-cell, it 
penetrates into the body of the latter, drains it, and, continuing to grow, produces 
fresh hair-like tubes, which attack other green Euglen®, often linking together 
dozens of them (see fig. 33°). In this way the Polyphagus grows apace and 
becomes a comparative large oblong vesicle, whilst the protoplasm within it divides 
into a number of parts. These, again, turn into swarm spores, with long ciliary 
filaments, and they slip out of the vesicle and may attack fresh Euglenz. 
Curiously enough, even saprophytic water-plants destitute of chlorophyll are 
sometimes attacked by parasites, and that, indeed, by species belonging ta the same 
group. Thus, for instance, the species of Achlya growing on the dead bodies of 
fishes and other animals which have perished in the water, are themselves infested 
by small parasitic Saprolegniacex and Chytridee. The example of these minute 
parasites represented in fig. 33° is named Rhizidiomyces apophysatus, and its 
host is Achlya racemosa. The swarming spores of the parasite lay themselves, 
in the manner described in previous instances, upon the spherical oogonia of A chlya, 
and insert extremely fine hair-like tubes into the interior of the cells attacked. 
These ramify like roots in the Achlya-cells, exhaust them of nutriment, grow 
perceptibly, and at length form spherical swellings, which, after reaching a certain 
size, break through the walls of the host-cells, project from the opening, and, 
lastly, push out in each case a sporangium. The latter produces a number of 
swarm-spores, which escape into the water and are able to seek fresh prey. 
We cannot here enter into details respecting the other kinds of reproduction 
occurring in the minute fungi parasitie upon hydrophytes. This is the right place, 
