48 



MICROBES, FERMENTS, AND MOULDS. 



wasp, because it is attacked during its lifetime by 

 a fungus which it cai'ries about for some time, and 

 which finally causes its death : this is Torrubia 

 spherocephala (Tulasne). Isaria sphingum, another 



Fig. 21. Two fVaments of Sapro- 

 legnia containing spores (greatly 

 magnified). 



Fig. 22. Oogonium of Saprolegnia 

 surrounded by Antheridia (much 

 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, 



