28 
MALARIA 
about 50 hours after the infective feeding. 
The pigment was coarse. De Buck (1935) 
found small oocysts after six days. Mayne 
(1932) followed the development in A. 
punctipennis (at 72° F. with 84 per cent 
humidity) in which, on the fifth and sixth 
days, pigmented oocysts measuring from 11 
to 15 micra were found. 
Many workers believe that the parasite 
species can be differentiated by the pigment 
in the young oocysts. According to Ste¬ 
phens and Christophers (1904) the young 
oocysts of P. malariae have rather coarse 
pigment which tends to clump. Gibbons 
(1933) believed that he could identify the 
species of the oocysts found in naturally 
infected mosquitoes. According to this 
author, the P. malariae pigment was dark 
brown or black, coarse and clearly visible 
irregular rods, usually 6 to 8 in number, 
and occasionally up to 12. The pigment 
was arranged in a straight or curved line, 
in a clump or rarely scattered around the 
oocyst. On one occasion he found the pig¬ 
ment to be light brown. Christophers, Sin- 
ton, and Coveil (1936) state that the 
younger oocysts are about the size of red 
blood corpuscles, the pigment has a dancing 
movement and resembles that seen in the 
gametocytes. They described the pigment 
as coarse and clumped; it was usually black 
but sometimes it was as light as in P. vivax 
or might have a greenish tinge. 
Mer (1933) followed P. malariae through 
A. elutus at 23-26° C. After 12 days the 
oocysts measured from 8 to 15 micra; the 
pigment was commonly distributed on the 
periphery. The oocysts were transparent 
and easily overlooked. Mayne (1932) after 
15 days found a heavily pigmented oocyst 
measuring 7 micra in diameter. After 12 
to 13 days at 23° C, Kligler and Mer 
(1937) found oocysts in A. elutus measur¬ 
ing 5 to 10 micra. 
Stephens and Christophers (1904) say 
that the species of the older oocysts (40 to 
60 micra) are - indistinguishable. This is in 
agreement with Hylkema (1920) who states 
that as the oocysts become larger the pig¬ 
ment becomes finer and then disappears. 
On the twenty-first day, Mayne (1932) 
found unpigmented matured oocysts, with 
sporozoites, measuring 50 to 59 micra. Mer 
(1933) found oocysts up to 60 micra in 
diameter, with active sporozoites, after 28 
days. Hylkema (1920) found mature 
oocysts, containing sporozoites, after 10 to 
11 days which measured about 50 micra. 
He used mosquitoes caught in nature, and, 
although he seems to have eliminated the 
probability of natural infections, this possi¬ 
bility should not be overlooked. 
Most workers have found relatively few 
oocysts developing after experimental feed¬ 
ings. However, de Buck (1935) found one 
exceptional A. maculipennis var. atro- 
parvus which had about 150 oocysts. 
The oocysts do not develop at a uniform 
rate, even in the same mosquito. It is not 
surprising, therefore, that various growth 
rates of these developmental forms were 
noted in different mosquitoes under varying 
conditions. 
Sporozoites. When fully mature, the 
oocysts burst, releasing the sporozoites into 
the body cavity. These forms then shortly 
invade the salivary glands. 
Mer (1933) gives the following compara¬ 
tive sizes for the sporozoites: P. vivax, 8 
(micra ?), P. falciparum, 9, and P. ma¬ 
lariae, 11. In the latter the extremities 
were more curved and the movements more 
active. Mayne (1932) found the uniform 
measurement of around 200 sporozoites, 
from the glands, to be 13.2 micra. 
Boyd (1935a) claimed that P. malariae 
sporozoites are the coarsest and had the 
most diffuse chromatin. The diameter of 
the chromatin was sometimes greater than 
that of the cytoplasm. The extreme vari¬ 
ations in length were between 6 and 15 
micra. The length was from 10 to 30 times 
the diameter. While he noticed vibratory 
movements of masses of sporozoites in fluid 
preparations of the stomach, he never ob¬ 
served any locomotive motility in unfixed 
preparations from the glands. Identifica¬ 
tion of the species of sporozoites on mor¬ 
phological grounds, he believes, would be 
unreliable. Christophers, Sinton and Coveil 
(1936) concur in this opinion. 
Length of Cycle in Mosquito. It is well 
