124 HUGH GLASGOW. 



made from these into bouillon, all the abnormal forms regularly 

 appeared, as they had in the cultures direct from the caeca. 

 Since each colony in the plates contained only descendants of a 

 single bacterial cell, it became very evident that the apparent 

 contamination from the ca?ca of the squash bug was nothing- 

 more than an extreme case of the production of involution 

 forms, and that but a single organism had ever really developed 

 in cultures from the caeca of these insects. This established 

 conclusively the fact that we had but one organism to consider 

 in the culture from the caeca of Anasa tristis although it did not 

 show beyond question that this one organism was really the 

 true caecal bacillus. In view of the results from the culture 

 experiments with Murgantia, however, it certainly seemed prob- 

 able that this was the caecal bacillus. 



One fact which made this view rather uncertain for a time 

 was that in 1895 a generally distributed disease of the squash 

 bug was discovered by Duggar in the neighborhood of Urbana. 

 This disease appeared to be fairly common, and was described 

 as affecting principally the fat body and the perivisceral tissues 

 generally. There was a distinct possibility that a chronic form 

 of this disease might be present among the apparently healthy 

 bugs that had been used in the culture tests just described, and 

 that the growth in these cultures was really due to this organism 

 from the fat body contaminating the caeca as they were removed 

 from the insect for inoculation. 



No more insects were available for testing this theory, but the 

 following season several large series of culture tests were carried 

 out with this point in view, two tubes being inoculated from each 

 insect in the following manner: Upon opening the abdomen a 

 large lobe of the fat body adjacent to the caeca was removed, 

 before the alimentary canal was broken, and placed in one of 

 two tubes of bouillon. A section of the caecal system was then 

 removed and put into the check tube. Without discussion of 

 detail, it is enough to say that as a result of several hundred 

 such tests growth was obtained from the caeca in every case, 

 while the tubes inoculated from the fat body invariably remained 

 sterile. 



In order to ascertain the distribution of the caecal bacteria 



