The development of small pyriform merozoites of B. bovis in the granule-secreting cells of the
salivary glands of B. microplus larvae, studied with a light microscope, showed a close resemblance
to that of B. argentina described by Riek (1966) in the same tick vector. Development took place
through a process of schizogony and resulted in the formation of many merozoites. A study of the
ultrastructure of developing merozoites in the schizont revealed the following: a poorly defined outer
membrane; a granular osmiophilic inner membrane; anterior and posterior polar rings; rhoptries;
micronemes; microtubules; a nucleus; spherical bodies of varying size. The schizonts were membrane-bound
but no parasitophorous vacuoles were seen.