The Mastigophora 177 



Leptomonas Kent (Fig. 4. 41, A, B) includes parasites of invertebrates. 

 However, the type species — Leptomonas bhtschlii Kent from the gut of 

 a nematode {Trilobiis gracilis) — has not been studied in detail and it is 

 not yet certain that more recently erected species actually belong in Kent's 

 genus. According to current concepts of the genus, both haptomonad and 

 nectomonad leptomonads may occur in the digestive tract and leishmanial 

 stages are to be expected in the posterior intestine. The leishmanial 

 forms of L. ctenocephali, which become resistant to desiccation (284), 

 are voided in the feces and ingested by flea larvae. The infection persists 

 through development of the flea (68). 



Phytomonas Donovan. Members of this genus occur in invertebrates 

 and plants. Phytomonas davidi (85) is found as leptomonad and leish- 

 manial forms in the latex of Euphorbia segetalis and in the digestive tract 

 of a bug, Stenocephalus agilis, which feeds on the plant. After a period 

 of multiplication in the insect, leptomonad stages appear in the salivary 

 glands. These are presumably the forms infective for plants. In addition, 

 transfer of leishmanial stages from insect to insect has been reported. 



Leishmania Ross (Fig. 4. 41, C, D). The life-cycle involves a vertebrate 

 and an invertebrate host. In mammals, the leishmanial form is predom- 

 inant, or else the only stage found, and occurs primarily in lymphoid- 

 macrophage cells, and occasionally in mononuclear and polynuclear 

 leucocytes of the peripheral blood. Leishmanial stages ingested by the 

 invertebrate hosts (species of Phlebotomus) develop into leptomonad 

 forms which multiply in the digestive tract. Infective stages are eventu- 

 ally inoculated into a vertebrate. Leishmania donovani, L. tropica, and 

 L. brasiliensis, which are parasitic in man, are discussed in Chapter XII. 

 Leishmania chamaeleonis, in contrast to the typical species of mammals, 

 occurs both as leptomonad and leishmanial forms in the cloaca of a 

 chameleon (285). 



Crithidia Leger (Fig. 4. 41, E-G). Crithidial, leptomonad, and leish- 

 manial forms occur in the invertebrate hosts. However, the leptomonad 

 forms may be mere transitory stages in fission or in development of 

 crithidial and leishmanial forms. The type species, C. fasciculata, was 

 described from the intestine of Anopheles maculipennis (180). Leish- 

 manial stages, produced in the hind-gut, apparently are eliminated and 

 then ingested by new hosts. The occurrence of infections with C. lepto- 

 coridis in nymphs of the box-elder bug (188) indicates that insects may 

 become infected before the adult stage is reached. 



Herpetomonas Kent (Fig. 4. 41, M-R) is limited to invertebrates, but 

 the life-cycle includes trypanosomal forms as well as the other types. 

 Detailed studies of the type species, H. muscarum (Leidy) Kent — some- 

 times known as H. muscae-domesticae (Stein) Kent — have shoAvn that 

 trypanosomal stages occur in flies (283) and in cultures (68). Leishmanial 



