INFECTION OF Jl Kltl'KTOMONAS 177 



powerful argument in favour of the tiagellate origin of the Sporozoa, 

 which he had previously suggested, and which Butschli had put 

 forward in 1884. After the degeneration of the Hagcliuni a 

 thickened gelatinous covering is formed, containing a double row 

 of gi'anular botlies (X(t), and these cysts are regarded by Patton 

 as the post-fiagellate stage. Wenyon {I.e.) finds that nuclear 

 multiplication may occur during encystment. Dunkerly (1911) 

 describing the life-history of a flagellate under the name of Lepto- 

 monas miiscae-domesticae, to Avhich reference is made later, records 

 the occurrence in the rectum of flies of small oval bodies similar in 

 appearance to these cysts ; they were found near the rectal glands, 

 and flies containing these cysts contained no flagellate forms. 



The cysts pass out with the faeces of the fly and dropping on 

 the moist window pane or on food are taken up by the proboscides 

 of other flies which are thus infected. 



Prowazek describes dimorphic forms of the flagellate stage, 

 which he regards as sexually differentiated forms, but Patton, in a 

 letter to me, says that he is unable to find any of these com- 

 plicated sexual stages. According to Prowazek, one of these forms 

 is slightly larger than the other, and has a gi-eater affinity for 

 stain. The dimorphic forms conjugate ; their cell substance and 

 nuclei fuse, and a resting-stage cyst is formed, but the subsequent 

 stages have not been followed. He further states that the sexually 

 differentiated forms may force their way into the ovaries where 

 they undergo autogamy and infect the subsequent brood. Mackinnon 

 in her study of Herpetomonas was unable to find, after a careful 

 search, any infection of the ova. She never found any larval 

 infection in M. domestica, but it was commonly found in Scato- 

 phaga and Fannia. It is suggested that the infection of the adult 

 fly is probably fresh and is independent of that of the larva. 



In Madras Patton found that 100 per cent, of the flies were 

 infected with the flagellate ; Prowazek found it in 8 per cent, of 

 the flies at Rovigno. In the cold season in the plains (India) 

 Lingard and Jennings (I.e.) found the flagellate in less than 1 per 

 cent, of the flies examined ; in the hills (Himalayas), at an eleva- 

 tion of 7500 feet, the flagellates were most numerous during the 

 hottest season of the year, and gradually decreased in number to 

 October and November, when none were discovered. Wenyon 



H. H.-F. 12 



