510 . MARY B. STARK 



below the place of inoculation and in the other fly it was deep 

 in the thorax, between the muscles, and spreading into one of 

 the muscles. Both growths were deeply pigmented and looked 

 very much like old tumors of the larvae, where the cells have 

 become so crowded with pigment that the cell outlines are en- 

 tirely lost. Figure 1 shows a section through the center of the 

 tumor. Near the periphery of the growth may be noticed cells 

 that are not so densely pigmented. These cells resemble those 

 of the tumor originally injected and evidently must have de- 

 veloped from the injected tumor cells. That the tumors could 

 be kept alive and could even increase in size in a medium outside 

 the body of the fly larva was ascertained in the spring of 1916, 

 when very young tumors were removed from larvae and placed 

 in a hanging drop of sterile Locke's solution, sealing the cover- 

 slip with vaselin. In this condition the tumors were kept alive 

 for several days, during which time a perceptible increase in 

 size was noticed, also a change from a light tumor to a dark 

 mature tumor by the increase in the amount of pigment. If 

 only a portion of the tumor was placed in the hanging drop 

 there was an irregular spreading of the cells as growth continued. 



The mortality due to the operation was considerably decreased 

 by repeating the last experiment under absolutely aseptic con- 

 ditions. The tumors of larvae bred on sterile media in Erlen- 

 meyer flasks, and the flies operated upon were also reared on 

 sterile media. Table 1 gives the results of this experiment. 



One hundred and eighty-two flies were operated upon. Of 

 these, seventy-three died from the effect of the ether. The 

 forty flies that died within twenty-four hours were never very 

 active and probably died from the effects of the operation. 

 The remaining sixty-nine flies recovered from the operation and 

 were very active and normal in their behavior until just before 

 death, when they became sluggish and inactive. Of these, 

 twenty-nine died within forty-eight hours, thirteen within three 

 days, six within four days, and twenty after one week. Of the 

 flies that recovered from the effects of the ether, 36.69 per cent 

 died from the operation and 63.30 per cent died from the effects 

 of the tumor suspension. 



