130 HUGH GLASGOW. 



they still have the appearance of ordinary bacteria. As in the 

 two preceding forms they occur typically in pairs and show no 

 motility. The individuals of these pairs average about 4 by 0.9 

 microns, while some may be considerably longer. Individual 

 rods, which are often slightly bent, may be as long as 8 microns 

 while short rods no longer than 1.5 microns are frequently 

 present, although these different forms all grade insensibly into 

 one another. 



In Peribahis limbolarius (Plate VIII., Fig. 25) the bacteria are 

 very much longer than in Euschistus sermts, and while they still 

 tend to appear in pairs this feature is not so marked as in the 

 three cases mentioned above. The individual cells are remark- 

 ably long, varying from 5 to 50 microns long by about 1.2 microns 

 in. diameter. The shorter rods often show a characteristic bend- 

 ing, the curve being very gradual and extending the full length 

 of the cell. This tendency is greatly exaggerated in the longer 

 elements, which are frequently bent several times, but even here 

 the curves are gradual and symmetrical, there being no sharp 

 twisting and distortion of the rods as in Murgantia histrionica, 

 and even in the longest, the diameter remains very constant 

 throughout. The extremely long elements are more common 

 in some individuals than in others, frequently making up a large 

 part of the caecal contents in such insects. 



When these organisms were first encountered I could hardly 

 believe that the extremely long, curved, thread-like structures 

 really represented single cells and not chains of closely packed 

 units, although no definite divisions could be made out either in 

 fresh or in stained preparations. When stained heavily and then 

 decolorized to a certain point these threads break up into irregular 

 bead-like granules which are scattered rather regularly through- 

 out. These granules clearly do not represent separate units, 

 however, as the same bodies likewise appear in the short rods 

 under the same manipulation, and these unquestionably repre- 

 sent single cells as do also the longer thread-like elements. 



The caecal organism of Murgantia histrionica (Plate VIII., 

 Fig. 26) is of such bizarre form that there is really little about it 

 to suggest its bacterial nature, and this might very well be ques- 

 tioned, in the absence of anything definite in the way of culture 



