3GG Illinois State Lahoratory of Natural History. 



tive than pure cultures made from it. To determine if 

 the oi'gan'sm was thus attenuated by continuous growth 

 in the laboratory, ten success! v^e cultures were made, the 

 first proceeding immediately from an isolation culture, 

 and the growth in each tube being permitted to mature 

 before the succeeding one was inoculated from it. The 

 first series was kept for one month, and the second series 

 was prepared from this just two days before the experi- 

 ment was to be made. At this time water-beetles were 

 not procurable, and adult squash-bugs were necessarily 

 used. The latter are rather difficult to operate upon, 

 and recover more readily than water-beetles; but the 

 relative activity of these solutions could be tested by 

 a comparison of the time required to produce the toxic 

 rigor. The results are indicated by the following table. 



Table VII. 



