364 Illinois State Laboratory of -Natural History. 



time decomposition would have advanced considerably. 

 In dilute squash-leaf decoction this beetle also survives 

 an immersion of many hours; and it is therefore evident 

 that the ingredients which might be dissolved from agar 

 cultures in making the infusions would play no part in 

 the result. In all subsequent cases the infusions were 

 obtained from agar cultures in slanting tubes, or from 

 the Petri dishes, by adding a small quantity of distilled 

 water, and then with the needle diffusing in this some 

 of the bacterial growth. This infusion was then trans- 

 ferred to. a deep Petri dish. 



It is probably well to give in detail the results of a 

 few experiments with this water-beetle. 



{a) Three minutes after immersion in an infusion from 

 an isolation culture the beetle became somewhat sluggish, 

 although it made a few rapid dives when touched, and 

 in ten minutes no movement could be induced. After re- 

 maining thus immersed five minutes longer, the beetle 

 was ti-ansferred to filter paper. Ten minutes later there 

 was slight sign of revival; but this was only temporary. 

 The insect in this case was immersed in an infusion from 

 pure cultures. 



{!)) In seven minutes rapid diving about the vessel 

 had ceased; in nine minutes there was only a slight 

 movement of the limbs; and in fifteen minutes the beetle 

 was apparently dead. It was kept in the infusion for 

 fifteen minutes after the toxic rigor was produced, and 

 was then removed to filter paper; but there was no re- 

 covery. 



(c) A tube culture was sterilized by exposing it to a 

 temperature of 125° F. for one hour on two successive 

 days. An inoculation from this tube showed that it was 

 perfectly sterile, and an infusion was then prepared, in 

 which a beetle was placed. Sluggishness was manifest in 

 seven mintites, and in fifteen minutes there was no sign 

 of life. Fifteen minutes thereafter the insect was re- 

 moved to filter paper; but the only sign of recovery was 

 a temporary twitching of the limbs. 



