THE H^MOFLAGELLATES AND ALLIED FORMS 315 



addition to these four types of active flagellates, there may occur 

 also non-flagellated individuals or with the flagellum rudimentary 

 namely, (5) long " gregariniform " individuals (Fig. 136, EG; 

 Fig. 137, q) and (6) oval or rounded Leis hmania-torms. The latter 

 may become encysted and function as the propagative stages. If 

 the four active forms are all distinct species, one and the same host 

 may have intestinal flagellates belonging to four different genera ; 

 if they are all phases in the development of one species, it becomes 

 a subtle point for discussion which of the four forms is to be regarded 

 as the " adult " generic type. 



71. 



FIG. 137. Flagellates from the digestive tract and Malpighian tubules of Dro- 

 sophtta confusa. a, b, c, Trypanosoma drosophilce, three forms, from the 

 Malpighian tubules; d q, various forms of Leptomonas drasophilcB from 

 the intestine : d, e, f, leptomonad forms ; g, crithidial form ; h, , transitional 

 forms from the preceding to j, k, the leptotrypanosome-forms ; m, n, small 

 crithidial (" barley-grain ) forms ; o, p, forms transitional from the preceding 

 to q, gregariniform individuals attached to the epithelium by a rudimentary 

 flagellum, the middle one of the three in process of division. After Chatton 

 and Leger (533). 



Not in every case, however, does such complexity of form occur in the 

 same host. The development of a typical leptomonad, such as L. (H.)jaculwn 

 of Nepa cinerea, as described by Porter (556), is of a comparatively simple 

 type, like that of Crithidia gerridis described above. Non- flagellated Leish- 

 mania-like individuals give rise to flagellates of the true leptomonad type, 

 which multiply by fission; these in their turn 'pass into a non-flagellatcci 

 condition in the hind-gut, there becoming encysted and being cast out with the 

 faeces to infect new hosts. Prowazek (557) has described in H. muscce-domes- 

 ticcs an extraordinary complication of male and female types autogamy, 

 parthenogenesis of female forms, and " etheogenesis " of male forms ; none 

 of these statements can be accepted as even probable until the weighty super- 

 structure of theoretical interpretation is supported by a more substantial 

 foundation of observed facts. Many of the stages described by Prowazek, 

 especially his so-called "etheogenesis," represent stages in the development of 

 distinct parasitic organisms not belonging to the group Flagellata ; compare 

 Flu, Dunkerly. 



