Contagious Diseases of Insects. 275 



tioned, a slender Bacillus, and another Bacillus-like form, of 

 which there will be further question hereafter, — a short, broad 

 form with rounded ends and a paler center, — but nothing re- 

 sembling the smaller Micrococcus. These organisms were quite 

 possibly all septic bacteria, derived from the deca,3'ing body of 

 the caterpillar. 



The first unmistakable culture of the Micrococcus of the 

 cabbage worm was made October 20, in a test tube of beef 

 broth infected from the blood of a larva about half grown, de- 

 cidedly pale, but far from dead. The slide representing the 

 blood of this larva is not stained, but is in good condition. 

 There were two bacterial forms visible in it, — a spherical Mi- 

 crococcus .7 fi in diameter, and, very rarely, a slender Bacillus. 

 The flask in which the culture was made was poured from a 

 stock flask into a sterilized tube from which the ping of cotton 

 had just been removed, plugged again, boiled thoroughly about 

 three minutes and left to cool completely. The blood was 

 obtained by snip])ing the skin of the back with sterilized 

 scissors, and drawing up with a fresh pipette a little of the 

 thick fluid exuding. The tube was infected in the usual man- 

 ner, and not examined until two days thereafter, when it was 

 found decidedly turbid, although not extremely so. The Mi- 

 crococci were strictly spherical, 1 ^ in diameter, very uniform 

 and abundant, usually in doubles, but often single. The slides 

 made were excellent and well stained, some violet and some 

 brown. The bacteria differed from their originals only in being 

 somewhat larger. Still they were not larger than the Micrococ- 

 cus of the cabbage worm is often found, especially in the intes- 

 tines. The check flask remained wholly clear. 



Four other successful cultures of this Micrococcus were 

 made, so similar in all respects to the preceding that it is not 

 worth while to repeat details. It must be admitted, however, 

 that the minute blood form did not certainly reappear in its 

 original size in any of my cultures, if we except one case where 

 its numbers were relatively so few (about 100 to the field with 

 a power of 1,000) that it is barely possible that all were intro- 

 duced in the original infection. This fact is capable of either 

 one of three interpretations : (1) We may suppose that the 

 proof is incomplete that these smallest spherules from the blood 



