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 Chytridiurn Ola, which 

 attacks the green cells of fresh-water CEdogoniae. Its roundish swarm-spores are 

 furnished each with one long cilium, and swim, searching about in the water until 

 they meet with an CEdogonium-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. 



PolypJiagus Euglence, a member of the Chytridese, is parasitic on the gi-een 

 cells of Euglense living in v^^ater. The swarm spores of this microscopic fungus 

 (see fig. 33^) are oval and fui-nished, like those of Chytridium Ola, M^ith a long 

 cilium. 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, di-ains it, and, continuing to grow, produces 

 fresh hair-like tubes, which attack other green Euglenae, often linkincf tocfether 

 dozens of them (see fig. 33^). In this way the Polyphagas grows apace and 

 becomes a comparative large oblong vesicle, whilst the protoplasm within it di\ddes 

 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 Euglenas. 



Curiously enough, even saprophytic water-jjlants destitute of chlorophj-ll are 

 sometimes attacked by pai-asites, and that, indeed, by species belonging to the same 

 group. Thus, for instance, the species of AcMya growing on the dead bodies of 

 fishes and other animals which have perished in the water, are themselves infested 

 by small parasitic Saprolegniacete and Chytridete. 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 oi Achlya, 

 and insert extremely fine hair-like tubes into the interior of the cells attacked. 

 These ramify like roots in the Achlj^a-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 prej^ 



We cannot here enter into details respecting the other kinds of reproduction 

 occurring in the minute fungi parasitic upon hj^di'ophytes. This is the right place, 



