282 Illinois State Laboratory of Natural History. 



usually in doubles, to broad ovals, with the transverse diame- 

 ter about three fourths the longitudinal, these likewise usually in 

 doubles. Occasionally pairs of doubles are joined end to end 

 in four's, but longer chains than these were not observed. The 

 micrococci frequently occurred upon the slide in patches of 

 fifty to one hundred, in which most of the individuals were 

 seemingly single. The ovals above mentioned have the same 

 transverse diameter as the spheres, differing only in length. 

 This diameter varies but little from .75 ^, although slightly 

 smaller singles are not infrequently found. Many of these 

 small, as well as larger, singles are scattered separately through 

 the field. Besides the ovals above described, occasional ovals 

 larger than these are seen, closely resembling, in fact, Bacterium 

 termo, and probably to be considered as belonging to that genus. 

 These are about 1.5 ^ in length (doubles 3 /*) by 1 /t in trans- 

 verse diameter. 



In the thicker part of the film very considerable numbers 

 of excessively minute spherules were discernible, deeply stained, 

 .5 tt in diameter, apparently identical with those described under 

 Pieris rapce* on a preceding page*, and clearly the same as those 

 appearing in the culture described on page 286. 



The slide from which the above description is taken was 

 deeply stained with methyl violet July 30, and mounted in 

 dammar. 



Another slide, 4612, derived from the same lot of worms 

 and similarly treated, differs only in the fact that the micro- 

 cocci average somewhat smaller; that nearly every one is almost 

 strictly spherical; and that an occasional small Bacillus occurs, 

 2 /* to 3 ju in length by about .66 ^ in width. The ends are 

 broadly rounded, the sides parallel, except in the shorter speci- 

 mens where they are slightly convex. These bacilli are some- 

 times single, more commonly attached endwise in pairs. The 

 smaller oval forms, possibly distinct, frequently show a pale cen- 

 ter with ends heavily stained.f In this slide are a considerable 



*Is it perhaps possible that the silkworm affection had its excit- 

 ing cause in the disease of the cabbage worm, which made its first ap- 

 pearance in this region the year before ? 



I To this form a peculiar interest attaches in some of my other 

 studies, reported on a later page. 



