298 Illinois State Laboratory of Natural History. 



CONTAGIOUS CHARACTER OF THE DISEASE. 



I made no effort to determine experimentally the question 

 of the contagious character of this disease in Datana ministra, 

 and can only report that it gradually invaded all the breeding 

 cages of this and an allied species, Datana angusi, which we 

 found during the season. Many of these were kept at a dis- 

 tance from those suffering from the disease, either as reserve 

 or check lots, with the hope of protecting them from its oper- 

 ations ; but as they were, at farthest, in adjacent rooms, and as 

 we passed freely from one to the other, none of them can be 

 said to have been isolated. The bacteria appearing in the 

 walnut Datana (D. angusi) were not different from those 

 infesting the other species, except that in our observations the 

 spherical form was usually the characteristic one for this 

 species. Still, both spherical and oval micrococci were noted 

 in a multitude of instances. 



ARTIFICIAL CULTURES. 



Our first culture illustrating this disease was commenced 

 September 6, 1883, with material obtained from an example of 

 Datana angusi seriously affected, but not yet dead. The slide 

 made from the fluids of this larva is not by any means pure. It 

 shows in nearly equal quantities the spherical and oval micro- 

 cocci described in the preceding section, the oval form mostly 

 in doubles, each pair varying from 2.5 ^ to 3 /* in length, and 

 being .75 ^ in transverse diameter. The spherules were mostly 

 in doubles (the pairs somewhat under 2 /* in length) and in 

 chains of four or more, the elements of which were sometimes 

 quadrate. Many of both ovals and spheres were aggregated 

 in large, dense patches. Very rarely, also, occurred a larger 

 form, not measured, apparently a Bacterium. 



Sterilized and neutralized infusion of beef was infected 

 with fluids from this larva, by the methods and with all the 

 precautions already described. This infusion speedily became 

 milky, and slides made a few days after the culture was begun 

 show clearly a reproduction of the spherical Micrococcus of the 

 original fluid, but of no other form. In size, general appear- 

 ance, and reaction to staining fluids, this differed in no par- 



