SEXUAL PARASITES IN MALARIA 21 



not unlike full-grown parasites before any indication of 

 sporulation has taken place. When nearly full-grown 

 they can be distinguished from these, because there is 

 always a rounded space enclosed in the parasite free from 

 pigment and slightly more refractile to light ; through 

 the cytoplasm of this the pigment is scattered. These 

 forms may be found at any period, and are usually less 

 numerous than the schizonts. They undergo no further 

 development in the peripheral blood. 



In the shed blood further development takes place, and 

 can be observed in a thin blood film under the micro- 

 scope. The sexual forms, gametocytes, are potentially 

 male and female in the freshly shed blood, but it is 

 practically impossible, in the parasites of benign tertian 

 and quartan, to distinguish at first the males from the 

 females. After a short time, if the blood has been exposed 

 to air or has had water added to it, and still more rapidly 

 in the stomach of the mosquito, they become sexually 

 active. 



Sexual Multiplication. The first change that can be 

 seen is that the parasites become more definitely rounded 

 and the pigment appears to be in active movement, 

 indicating movements in the protoplasm. The remnants 

 of the red corpuscles w 7 hich had enclosed them disappear. 



In both male and female forms the next stage is the 

 extrusion of a considerable part of the protoplasm, so 

 that there are two bodies of unequal size, the smaller 

 being the polar body. The females ordinarily do not 

 undergo any further change, as seen on the slide ; they 

 are now in the receptive condition awaiting fertilization, 

 and are called macrogametes. The males do change. 

 In the larger of the two masses, into which the parasite 

 has divided, violent movement of its pigment occurs, and 

 it suddenly projects three, four, or five thin, long flagella, 

 which are free from pigment and actively motile, lashing 

 the neighbouring red corpuscles. These flagella, known 

 as microgameteSy are the male fertilizing elements, the 

 equivalent of spermatozoa. After a time they detach 



