54 



patient has already developed an immunity against 

 the fever - producing young parasites (spores). 

 Thus it is well known that in malignant tertian 

 the sexual forms, gametes or crescents, first appear 

 about a week to ten days after the first febrile 

 attack. If this view be true, then it follows that 

 the gametes develop from forms already present in 

 the system, viz., the asexual forms, and possibly the 

 divergence into sexual forms takes place from the 

 youngest form of the parasite, i.e., the spore. But 

 it is possible that the divergence takes place at a 

 stage previous to the youngest form of parasite, 

 i.e., at a stage immediately succeeding the entry 

 of sporozoits into the blood, so that we have from 

 the first asexual and sexual forms present. Sexual 

 development has been supposed to proceed mainly 

 in the internal organs, e.g., bone marrow ; but it 

 is being gradually recognized that young forms of 

 gametes are also found in the circulation ; the 

 characters of these have already been noted (p. 35). 

 Let us suppose, however, that we are now dealing 

 with fully developed gametes in the blood. We 

 shall proceed to describe the further changes 

 undergone in the mosquito. The male cell is, as 

 we have seen, called the mikrogametocyte ; the 

 female cell, the makrogamete. These we can 

 distinguish in the blood. Further flagellation can 

 be observed, i.e., the protrusion of so-called 

 'flagella,'i.e., mikrogametes or spermatazoa. These 

 'flagella' break off and fertilize the female cell, 

 the makrogamete, a process which has been seen 

 in halteridium of birds, but only once in man. 



This fertilized female cell or egg is known as a 

 Zygote, though it is more convenient to reserve this 

 term for a little later stage, and to call this stage 



