302 ENTOMOLOGY 
investigators thought to be due to different species of para- 
sites; and when, as often happens, the malarial chill occurs 
every day, this is attributed to two sets of tertian amcebule, 
sporulating on alternate days. 
After several successive asexual generations, there are pro- 
duced merozoites which develop—no longer into schizonts— 
but into sexual forms, or gametes. These occur in red 
blood corpuscles either as macrogametes (female, 7, 8) or as 
microgametoblasts (male, 7a, Sa), in which forms the parasite 
is introduced into the stomach of a mosquito which has been 
feeding upon the blood of a malarial patient. The macro- 
gamete now leaves its blood corpuscle and becomes spherical 
(9), as does also the microgametoblast (oa) ; but the latter puts 
forth a definite number (sir, in P. precox, 9b) of flagella, 
or microgametes, which separate off as motile male bodies, 
capable of fertilizing the macrogametes. A muicrogamete 
penetrates a macrogamete (70) and the nucleus of the one 
unites with that of the other. The fertilized macrogamete now 
becomes a migrating cell, or odkinete (rr), which penetrates 
almost through the wall of the stomach of the mosquito (72) 
and then becomes a resting cell, or cyst. This odcyst (13) 
grows rapidly and its contents develop, by direct nuclear divis- 
ion, into sporoblasts (14, 15), which differentiate into spindle- 
shaped sporozoites (16, 1). The sporozoites are liberated into 
the body cavity of the mosquito, carried in the blood to the sali- 
vary glands (as well as elsewhere) and thence along the hypo- 
pharynx into the body of a human being, bird or other animal 
attacked by the insect. 
The role of the mosquito as the intermediary host of mala- 
rial organisms was discovered by Manson and Ross and con- 
firmed by Koch, Sternberg and others. It has been found 
repeatedly that certain mosquitoes (Anopheles) after feeding 
on the blood of a malarial patient can transmit the disease by 
means of their “ bites’ to healthy persons. Thus, Anopheles 
mosquitoes were fed on the blood of malarial subjects in Rome 
and then sent to London, where a son of Dr. Manson allowed 
