STRUCTURE AND LIFE-HISTOEY OF ORITHIDIA MELOPHAGIA. 211 



P. C. Flu (1908) published an account of the flagellate 

 under the name of Crithidia melophagia. Flu stated that 

 he saw parasites in the ovaiy of Melophagus, and small 

 forms in the larva, but was unable to determiue the mode of 

 infection of the host. 



L. D. Swingle (1909), working in Nebraska, wrote a 

 description of the parasite, calling it C. melophagi. From 

 a private communication I learn that Swingle's work was 

 completed, but not published, before Flu's paper appeared, 

 thus accounting for the specific name melophagi (described 

 as new), which cannot stand. The chief value of Swingle's 

 work lies in the fact that he described rounded and 

 '' Plasmodia! " stages of the parasite as occurring in the egg 

 of the host. 



While Swingle was working in Nebraska, I was investiga- 

 ting the parasite independently in England. It gives me 

 gi-eat pleasure to be able to confirm Swingle's work, and to 

 add many more details concerning the modes of infection of 

 the parasite and its general life-history. 



Summary. 



(1) Crithidia melophagia is a flagellate occurring in 

 the alimentary tract, ovaries, ova, and puparia of Melo- 

 phagus ovinus. 



(2) The parasite has three stages in its existence, a p re- 

 flagellate stage (PI. 12, figs. 1-20), passed chiefly in the crop 

 and fore-gut of the insect host, a flagellate stage (PI. 12, figs. 

 21-44), occurring chiefly in the posterior two thirds of the 

 gut, and a post-flagellate stage, occurring either in the 

 rectum and fasces (PI. 13, tigs. 97-114) or in the ova and 

 pupa? (PI. 13, figs. 57-94). 



(3) The pre-flagellate stage is passed through very rapidly. 

 These parasites are small, usually oval bodies, Iju to 4'5 ju by 

 4'5 ju to 6 /LI, with round nuclei and bar-like blepharoplasts. 

 The flagellum arises near the blepharoplast from a chromato- 

 phile area. Division of pre-flagellates may occur (PI. 12, fig. 4) . 



