LIFE-HISTORY OF LEPTOMONAS MUSC/R PtOMESTTCF. 651 



of a vertebrate. But no forms were then known witli an 

 undulating membrane in a truly non-sanguivorous insect. 

 In 1908, however, Chattou and Alilaire (2) described flagel- 

 lates found in Drosopliila conf usa— a Leptomonas (:is 

 distinct from Prowazek's Herpetomonas) and a Trypano- 

 soma without a clear undulating membrane, but with the 

 blepharoplast at the posterior end of the body. They named 

 these forms L. drosophila) and T. drosophila?, but at the 

 same time put forward the suggestion that they are really 

 two stages of the same life-cycle. Werner (24) in 1909, and 

 Rosenbusch (21) in 1910, have stated that there are two 

 distinct parasites of the house-fly, a Herpetomonas of Piowazek 

 and a Crithidia with posterior kinetonucleus, of which Rosen- 

 busch describes the ency station. Roubaud, in an interesting 

 article in 1909 (22), has used an old generic term, "Lepto- 

 monas," for the uniflagellate parasite of the fly Pycnogonuni, 

 excluding Herpetomonas of Prowazek, which he also found 

 in the same fly. He regards, then, Herpetomonas of Pro\v!tztd< 

 as biflagellate, and Leptomonas as uniflagellate, with kineto- 

 nucleus usually anterior, but with a so-called trypiinosome 

 stage in its life-history. The evidence of Rosenbusch (21), 

 Chatton and Alilaire (2), and Mackinnon (14), and that given 

 by my figures, all goes to show that a form resembling 

 Leptomonas of Saville Kent is found in non-sanguivorous 

 Hies (in three cases, house-flies), developing in the course of 

 its life-history a form i-esembling a cultural trypanosome, and 

 having an encysted stage. Tlie fact that many observers 

 have seen a large form (shown in PI. 31, fig. 1), which differs 

 very much in appearance from Leptomonas, renders it possible 

 that the other observers who fail to see the two flagella are 

 dealing with a different organism. 



This much, however, seems certain : (1) That Leger's 

 original pear-shaped Crithidia is only a stage of the Lepto- 

 monas life-history; also (2) that the "Crithidia" of latei- 

 authors— Patton (18), Woodcock (25) — found in blood-sucking 

 flies, or in cultures, are in some cases developmental stages of 

 a Trypanosoma. The evidence of the forms found by me 



