In a previous paper (Hawking et al., 1968) it has been shown that with malaria parasites exhibiting a periodic synchronous asexual cycle (e.g. Plasmodium knowlesi; P. cynomolgie and P. cathemerium), the gametocytes show a 24 or 48 hour rhythm in their development to maturity and that this maturity is short lived (6–12 hours). In the present work, exflagellation of the male gametocytes of Plasmodium falciparum was studied quantitatively in 4-hourly blood films taken from 5 infected children in Gambia, West Africa. In 2 cases there was clear evidence of a 48 hour cycle in the number of exflagellations observed; in 2 cases there was a “probable” cycle present, and in 1 case there was a “possible” cycle although the evidence is not decisive. It is concluded that the gametocytes of P. falciparum probably resemble those of other periodic plasmodia in showing a (48 hour) rhythm of development to maturity (taking into account the well known irregularity of P. falciparum). The development of gametocytes of P. falciparum was also studied in Aotus monkeys. The classical view was confirmed that development from the merozoite takes more than 9 days and that there is no evidence for cell division during this process.
Hawking et al. (Fri,) studied this question.