5^ THE INVERTEBRATA 



to vertebrates owing to the latter being subject to attack by the original 

 hosts. The original mode of infection was by faeces. The species of 

 each genus assume, in certain circumstances, the forms characteristic 

 of other genera. The following are the principal genera. 



Herpetomonas (= Leptomonas) . Basal granule and parabasal body 

 at one end, near the origin of the flagellum. Parasitic in the gut, 

 principally of insects, but also of other invertebrates and of reptiles. 



Leishmania. Oval bodies containing a nucleus, parabasal body, 

 basal granule and rhizoplast, but with no flagellum, infesting the 

 tissues of vertebrates, and transferred by flies of the genus Phleboto- 

 mus, in whose gut they assume the form of Herpetomonas . In man they 

 cause kala-azar and Oriental sore. 



-fl- 



-p.by. 



A V C V D 



Fig. 48. A diagrammatic comparison of various Trypanosomidae. A, Her- 

 petomonas. B, Leishmania. C, Crithidia. D, Trypanosoma, ba.gr. basal 

 granule ;y?. flagellum; nu. nucleus; p.by. parabasal body; u.me. undulating 

 membrane. 



Crithidia (Fig. 47 F). Flagellum starts from a basal granule near 

 the middle of the long, slender body, to which the flagellum is united 

 by an undulating membrane; parabasal body placed between the 

 basal granule and the nucleus. Parasitic in the gut of insects. 



Trypanosoma (Fig. 47 E). As Crithidia, but the basal granule 

 of the undulating membrane and the parabasal body are beyond the 

 nucleus, towards the non-flagellate end, so that the disposition of the 

 flagellum recalls that of the trailing flagellum of Bodo. Many species, 

 all parasitic in the blood and other fluids of vertebrates, and nearly 



