<unk>  species are unicellular eukaryotes having a well-defined nucleus and other cell organelles including kinetoplasts and flagella. Depending on the stage of their life cycle, they exist in two structural variants, as: #The amastigote form is found in the mononuclear phagocytes and circulatory systems of humans. It is an intracellular and nonmotile form, being devoid of external flagella. The short flagellum is embedded at the anterior end without projecting out. It is oval in shape, and measures 3–6 µm in length and 1–3 µm in breadth. The kinetoplast and basal body lie towards the anterior end. #The promastigote form is found in the alimentary tract of sandflies. It is an extracellular and motile form. It is considerably larger and highly elongated, measuring 15-30 µm in length and 5 µm in width. It is spindle-shaped, tapering at both ends. A long flagellum (about the body length) is projected externally at the anterior end. The nucleus lies at the centre, and in front of it are the kinetoplast and the basal body. L. infantum amastigote forms
Leishmania
Plasmodium
Trypanosoma
Boswellia
Echinostoma
Acheiropodia
Cryptosporidium
Microfilaria