PARASITIC ORGANISMS. 15 
mean time, we turn to the study of forms of life in many respects 
intermediate between plants and animals, and full of practical 
interest for mankind, on account of their relations to disease, 
as revealed by recent investigations. 
PARASITIC ORGANISMS. 
THE FUNGI. 
Mo tps (Penicillium Glaucum and Mucor Mucedo). 
Closely related to Torula physiologically, but of more com- 
plex structure, are the molds, of which we select for convenient 
study the common green mold (Penicillium), found growing in 
dark and moist places on bread and similar substances, and the 
white mold (Mucor), which grows readily on manure. 
The fungi originate in spores, which are essentially like 
Torula in structure, by a process of budding and longitudinal 
extension, resulting in the formation of transparent branches 
or tubules, filled with protoplasm and invested by cellulose 
walls, across which transverse partitions are found at regular 
intervals, and in which vacuoles are also visible. 
The spores, when growing thus in a liquid, give rise to up- 
ward branches (aérial hyphce), and downward branches or root- 
lets (submerged hyphe). These multitudinous branches inter- 
lace in every direction, forming an intricate felt-work, which 
supports the green powder (spores) which may be so easily 
shaken off from a growing mold. In certain cases the aérial 
hyphe terminate in tufts of branches, which, by transverse 
division, become split up into spores (Conidia), each of which 
is similar in structure to a yeast-cell. 
The green coloring matter of the fungi is not chlorophyl. 
The Conidia germinate under the same conditions as Torula. 
Mucor Mucedo.—The growth and development of this mold 
may be studied by simply inverting a glass tumbler over some 
horse-dung on a saucer, into which a very little water has 
been poured, and keeping the preparation in a warm place. 
Very soon whitish filaments, gradually getting stronger, ap- 
pear, and are finally topped by rounded heads or spore-cases 
(Sporangia). These filaments are the hyphe, similar in struct- 
ure to those of Penicillium. The spore-case is filled with a 
multitude of oval bodies (spores), resulting from the subdivis- 
ion of the protoplasm, which are finally released by the spore- 
