MORPHOLOGY, LIFE CYCLE AND PHYSIOLOGY OF P. MALARIAE 
27 
(1939) in a mixed infection of P. malariae 
and P. falciparum found an unpigmented 
parasite contained in a basophilic mono¬ 
blast, but this was not shown definitely to 
be of P. malariae origin. Raffaele (1940) 
reports finding unpigmented forms, for the 
first time, of P. malariae in the bone 
morrow. 
Sporogonous Cycle 
Gametocytes. In the blood stream the 
young stages of the gametocytes of P. 
malariae are similar to the asexual forms. 
It is virtually impossible to distinguish a 
gametocyte from an asexual form until 
about the 54th hour, at which time the 
asexual form begins to show multiple chro¬ 
matin masses. 
From the 54th to the 72d hour, differenti¬ 
ation between the sexes of the gametocytes 
becomes more certain. The female exhibits 
a heavy deeply-staining blue cytoplasm with 
a small, eccentric, sharply-defined and well- 
staining chromatin mass. In the male gam¬ 
etocyte, the cytoplasm stains a light to pink¬ 
ish blue. The chromatin is diffusely scat : 
tered, sometimes occupying one-half of the 
cell, and stains a very light pink in contrast 
to the deep pink or red of the female. The 
pigment in both types of gametocytes re¬ 
mains scattered as long as the parasites 
remain in the blood stream. 
When fully grown, the gametocytes com¬ 
pletely fill the host cell. The gametocytes 
mature at or shortly after the segmentation 
of the asexual forms. The evidence so far 
indicates a cyclic development parallel to 
that of the asexual forms. 
Ordinarily more female than male gam¬ 
etocytes are produced. However, this may 
vary with different strains as de Buck 
(1935) believes that the Vienna strain pro¬ 
duces more male than female gametocytes. 
Many workers believe that gametocytes 
are rarely produced by P. malariae. Our 
studies on induced quartan malaria do not 
bear this out, for we have found them at all 
seasons and in all types of infections. How¬ 
ever, it is true that in absolute numbers few 
gametocytes are found, but it must be re¬ 
membered that this species has the lowest 
blood stream population density of the 
human malarias. 
Sporogony in Mosquito 
Because of the rarity of natural infec¬ 
tions, the scarcity of gametocytes, and the 
small number of mosquitoes which become 
infected, relatively few observations have 
been made on the developmental cycle of 
this species, and knowledge of the sporogo¬ 
nous cycle is far from complete. 
Maturation. When the mosquito ingests 
blood containing mature gametocytes, ma¬ 
turation of the female gametocyte occurs. 
This process has not been adequately ob¬ 
served for P. malariae. Following the 
maturation, the female gamete is ready for 
fertilization by a male gamete. 
The matured male gametocyte ejects sev¬ 
eral “flagella” which are the male gametes. 
Raffaele (1939) found the gamete consists 
of a tapering filament containing chroma¬ 
tin, with a long flagellum attached at the 
anterior end; this flagellum is more or less 
adherent to the filament throughout its 
length. 
It has been found in our laboratory that 
varying numbers of male gametes are 
formed when exflagellation occurs in a 
moist chamber, the number varying between 
two and five. 
In a moist chamber, Kligler and Mer 
(1937) found this species to be the slowest 
of all to “ exflagellate. ” Mer (1933) ob¬ 
tained better infections in Anopheles elutus 
when both young and fully-grown gameto- 
eytes were present than when only fully- 
grown gametocytes were found, although 
the latter “exflagellated” well. 
Fertilization, ookinete (vermicular zy¬ 
gote). Although the actual process of fer¬ 
tilization of other parasites has been wit¬ 
nessed, little specific information of this 
process in P. malariae is available. The 
same is true of the resulting mobile ookinete 
or vermicular stage. 
Developing oocysts. The developing 
oocyst is first seen as a clear oval or spheri¬ 
cal body containing pigment, located on the 
outer surface of the midgut. Hylkema 
(•1920) found oocysts measuring 5 micra 
