GASTRIC CECA OF THE HETKROPTERA. 125 



throughout the alimentary canal, cultures were made from 

 different sections of the midgut, including the first stomach, 

 third stomach and the csecal region. From a large number of 

 such tests it resulted that while growth invariably appeared in 

 the tubes from the caeca, and usually also from the third stomach, 

 only from ten to twenty per cent, of the inoculations from the 

 first stomach showed any growth, all the others remaining sterile. 



Cultures were repeatedly made from the eggs of Anasa tristis; 

 and upon comparison, it was found that the organism from this 

 source was certainly the same as that isolated from the caeca, 

 and it was also determined that this was the only organism that 

 ever appeared in cultures from the eggs of this insect. 



It was expected, in the beginning, that the bacteria from the 

 caeca of the Heteroptera, if they developed at all on artificial 

 media, would prove to be a number of very different forms, 

 perhaps occurring only in their respective insect hosts, and 

 when it was found that the organism isolated from the caeca 

 of Anasa belonged to so common a group a's the non-liquefying 

 fluorescent bacteria, it was feared that, after all, the form 

 isolated from this insect might have been merely the result of 

 a contamination of the alimentary canal by some of the ever- 

 present species of this group; although the fact that this same 

 organism was isolated regularly from the egg seemed very 

 conclusive. 



In order to show beyond question whether or not the bacteria 

 so regularly isolated from the squash bug were really the same as 

 those normally present in the caeca, it was planned to check the 

 cultures which had been obtained from the insects against the 

 bacteria direct from the caeca by means of the agglutination test. 

 Young rats were chosen as best suited for this work, as they are 

 much more hardy than young guinea pigs of the same weight. 

 The animals selected weighed only from fifty to seventy-five 

 grams, as it was feared that sufficient material for the immuniza- 

 tion might not be available in case large animals, such as full- 

 grown guinea pigs, were used. It was planned at first to im- 

 munize the animals to cultures of the bacillus isolated from the 

 caeca, and to test such sera against emulsions of the bacteria 

 direct from these organs, but owing to the fact that bacteria 



