516 MARY B. STARK 



nearly four weeks after the operation must have died from the 

 effects of the tumor-cell suspension. The tumors, if any had 

 developed, were too small to be seen through the thick exo- 

 skeleton of the meal worm. All these worms had been dead 

 too long for microscopical examination, and it cannot be said 

 definitely that tumors had developed in the last seven worms 

 mentioned. The meal worms seem more resistant to the inocu- 

 lation of the tumor-cell suspension, since 57.5 per cent of the 

 worms inoculated remained normal. It is to be expected that 

 the tumor cells cannot be transplanted successfully into all 

 insects. Erwin F. Smith has had the same experience with his 

 crown galls. Some plants, he found, are too resistant for the 

 development of the gall when cells of the same are transplanted 

 into them. (Johns Hopkins Hospital Bull., Vol. 28, 1917.) 



THE TUMOR NOT DUE TO AN INFECTION 



Since the tumor of Drosophila is hereditary — occurring ex- 

 actly in one-half of the males in every generation — it does not 

 seem probable that it is due to an infection. However, sus- 

 ceptibility to an infection may be hereditary. In that case the 

 infection is possible only in the presence of the microorganism to 

 which susceptibility is hereditary and the tumor could develop 

 only in the pl-esence of the specific microorganism. To deter- 

 mine whether the tumor is due to an infection or not, I made an 

 attempt to isolate a specific organism. I sterilized larvae with 

 tumors, removed the tumors, exercising all aseptic precautions, 

 and ground them into pieces in some Locke's solution. All the 

 ordinary laboratory media were inoculated with this cell sus- 

 pension and incubated under both aerobic and anaerobic con- 

 ditions. Twice I got a growth of B. subtilis, otherwise no growth 

 whatever. B. subtilis is a saprophyte commonly found in tu- 

 mors and is probably not the cause of this tumor. Before pre- 

 paring special media for the specific organisms that might be 

 the cause of the tumor, it occurred to me to cultivate the flies in 

 which the tumor occurs under aseptic conditions. Eggs were 

 picked and sterihzed in 85 per cent alcohol for ten minutes. 

 They were then transferred to sterile media in Erlenmeyer 



