288 Illinois State Laboratory of Natural History. 



stained unquestionably agreed in every particular with the com- 

 mon spherical Micrococcus of the original silkworm material, 

 except that it measured a trifle smaller, scarcely averaging 1 n, 

 although many individuals and doubles were fully that size. 

 This culture was preserved for experiment and used as an infec- 

 tion fluid on the 9th August. The results of this attempted 

 infection will appear under another head. 



Still another culture, commenced and examined upon the 

 same dates, yielded an abundance of the spherical Micrococcus 

 most frequently mentioned above, together with occasional 

 examples of a Bacillus 3 ^ or 4 /* in length and about 1 ^ in 

 transverse diameter. These last were, however, too rare to have 

 any special significance, except as a slight adulteration of the 

 culture. 



The next culture attempted, commenced July 31 and 

 examined August 4, is of especial interest, as it resulted in the 

 complete displacement of the normal Microcoocus of the silk- 

 worm by another organism present in its fluids (the question- 

 able Bacillus intrapallens already mentioned*), but in small 

 num bers. 



This culture was made from a silkworm of the original lot 

 received from Professor Burrill, July 30, the beef infusion being 

 infected from a dead worm. The fluids of this larva contained 

 vast numbers of the ordinary silkworm Micrococcus, somewhat 

 under the usual size, averaging, indeed, only about .75 /*. An 

 occasional large Bacillus, 4.5 ^ long and 1 ^ wide, also occurs 

 on the slides made from this individual. Besides the above 

 is the organism already mentioned, varying in form from a 

 broad oval to a Bacillus - like rod, characterized by a pale 

 center staining little or none, and heavily stained extremities. 

 The culture examined August 4 contained vast numbers of this 

 organism and apparently nothing else. Most of those appear- 

 ing in the films from this culture were much smaller than the 

 original, all the stages, in fact, appearing, from a simple sphere 

 scarcely, if at all, distinguishable from a Micrococcus, to the 



* This organism displaced similar cultures made from the larva of 

 Datana angusi presently to be reported on, was preserved through the 

 winter, cultivated the following season, and then applied effectively to 

 the destruction of larvae of other species. 



