(_a_) The first type--which possibly belongs to another organism, _Pneumocystis carinii_, see p. 90--occurs in the capillaries of the lungs. The flagellate parasite entering the lung capillaries loses its flagellum and undulating membrane. Its body becomes curved, and the two ends fuse, and so an oval mass is formed (fig. 33, _8_-_11_). In some cases the blepharoplast disappears, in other cases it blends or fuses with the nucleus. The nucleus of the rounded parasite then divides into eight by successive divisions (fig. 33, _12_-_15_). Next the body, which is surrounded by its own periplast, also divides, giving rise to eight tiny daughter individuals or merozoites (fig. 33, _15_). The merozoites lie inside the periplast, which acts as a sort of “cyst wall.” The merozoites are said to exhibit dimorphism, and Chagas has interpreted the dimorphism in terms of sex. The daughter forms, produced by the parent trypanosomes which kept their blepharoplasts, themselves have blepharoplasts as well as nuclei, and have been termed “males” or “microgametes.” The merozoites, arising from parent trypanosomes which lost their blepharoplasts, have themselves only nuclei, and have been called “females” or “macrogametes.” In the case of the so-called “female” forms the single nucleus divides into two unequal parts, of which the smaller becomes the blepharoplast, and a flagellum is formed later. The so-called “males” possess early a rudiment of a flagellum. Both kinds of merozoites escape from the parent periplast wall, and enter red blood corpuscles. They grow into flagellates within the corpuscles, and then become free as adult trypanosomes in the blood-stream. [Illustration: FIG. 34.--_Trypanosoma cruzi_. Transverse section of a striated muscle containing rounded forms of the parasite in the central portion. × 1,000 approx. (After Vianna.)] (_b_) The second mode of multiplication is one of asexual reproduction (schizogony or agamogony). It was first described by Hartmann from hypertrophied endothelial cells of the lungs. It has since been found in the cardiac muscle, in the neuroglia of the central nervous system, and in striped muscle (fig. 34). In laboratory animals it has also been found in the testicle and suprarenal capsules. In these tissues the parasite is intracellular, appearing as a small rounded body with nucleus and blepharoplast, without flagellum or undulating membrane. In other words the parasite is _Leishmania_-like in the body tissues, and recalls the organism of kala-azar.