312 



CHARLES T. BRUES AND RUDOLPH W. GLASER. 



of the insects. These vary considerably in size, ranging from 

 6-i6;u in length and from 3-9^ in width. They are thus more 

 variable in size in culture than in the insect and generally more 

 elongate. The maximum length is about the same, but there are 

 more smaller cells in culture, due no doubt to the fact that during 

 rapid development the buds separate when less fully developed 

 than in the insect. The internal structure when stained, appears 

 to be the same as that of the forms in the fat-body described 

 above. 



After prolonged incubation on solid media the formation of a 

 distinct mycelium always occurs. This is at first w T hite, but after 

 several w r eeks, blackened spots sometimes become visible, due to 

 the development of pigment in the walls of certain groups of 

 cells. This occurs especially on potato-agar. In at least one 

 liquid medium, Locke's solution, the same blackened cells develop. 



FIG. 2. Portion of mycelial growth of symbionts after prolonged incuba- 

 tion (10 days) in liquid bouillon medium. Magnified about 400 diameters. 



The mycelium (Fig. 2) is branched and of quite irregular 

 form. The larger hyphse measure from 6-i$p. in diameter, 

 broad and narrow cells frequently alternating or with one size 

 interpolated in series of the other. Some cells, usually single 

 ones or pairs, more rarely several in succession are heavily pig- 



