48 MICROBES, FERMENTS, AND MOULDS. 
wasp, because it is attacked during its lifetime by 
a fungus which it carries about for some time, and 
_which finally causes its death: this is Torrubia 
spherocephala (Tulasne). Isaria sphinguwm, another 
Fig. 21.—Two filaments of Sapro- Fig. 22.—Oogonium of Saprolegnia 
legnia containing spores (greatly surrounded-by Antheridia (much 
magnified). magnified). 
species of the same genus, has been observed on the 
back of a butterfly, which was poised upon a leaf as 
if alive, and which was probably killed by- the 
development of the fungus. 
These and other facts, not to speak of the 
muscardine of silkworms, to which we shall return, 
