Insects and Parasitic Diseases. 47 



111 the whole thirty-nine horses' stoniax.'hs exainiined, of which 

 nineteen contained tiiinours of H. niegastoma, I have never been 

 ^ble to find any stage, adult or otherwise, of H. muscae or H. 

 inicrostonia associated with such tumours — wdiich is in harmony 

 with the commonly accepted statement tliat these tumours are due 

 to H. niegastoma. For this reason, therefore, it has been considered 

 perfectly safe foi- experimental purposes to use the contents of such 

 tumours to infect sterile faeces with the eggs and embryos of H. 

 'Uiegasto-ma. 



A. To determine the intermediary host or hosts of H. megastoma 

 and the early life-history of the parasite. 



E.rperitnent No. 17. 



On October 25th the contents of a stomach tumour or nodule 

 •containing embryos were mixed with sterilized normal saline and 

 .sterilized faeces, and without a preliminary period of incubation 

 fed to four-days-old larvae of Musca domestica. All seventeen of 

 the resulting adult flies w^eie examint;d on November 6th, 7th and 

 -8th, of which number six contained from one parasite in one fly to 

 -eight parasites in three other flies. These parasites measured from 

 0.21 mm. to 0.95 mm. long. 



Erperiment No. 18. 



A similar experiment to No. 1 was commenced on November 26th 

 with three-days-old Musca domestica larvae. Three days later a 

 portion of the faecal matter was examined, and found to contain a 

 few^ living embryos. Subsequently (November 29th to December 

 10th), the resulting larvae, pupae and flies, fifty-two in all, w^ere 

 'examined with negative results. 



Erperiment No. 19. 



The contents of a stomach tumour were mixed witli saline and 

 .sterilized faeces on December 3rd, and incubated at a temperature 

 of 22^C. — 27'X\ for seven days. On December 10th and subse- 

 quently, five-days-old larvae of Musca domestica were fed on the 

 infected matter. On Decen^ber 18th living embryos w^ere still found 

 in the faeces. Between December ITtli and 21st, 8 larvae, 5 

 pupae and 77 adult flies were examined, of which number 3 larvae 

 and 42 flies were found to contain larval parasites. One or two 

 parasites, measuring 0.32 mm. -0.5 mm. long, were found in most 

 of the flies, but in one case, ten parasites measuring about 0.86 

 mm. long, were found, eight of whicli weie encysted. 



