SEXUAL CYCLE IN THE MOSQUITO 631 



the latter ; they accordingly consider that this is probably the 

 period necessary for the development of the sexual forms. They 

 also consider that the long persistence of crescents in the blood 

 after the fever has ceased, is due not to the long survival of 

 individual crescents, but to their being constantly replenished 

 from asexual forms which persist in the blood and pass through 

 the ordinary process of schizogony, fever only occurring when 

 the number of asexual forms reaches some hundreds per cubic 

 millimetre. 



It is well known that after a patient has apparently recovered 

 from malarial fever a relapse may take place without fresh 

 infection occurring, sometimes several years afterward, and 

 Schaudinn has published interesting observations bearing on 

 this point. He has found, and his observations on this point 

 have been confirmed, that the macrogametocyte of tertian fever 

 may by a process of parthenogenesis give rise to merozoites, 

 which in their turn infect the red corpuscles and start the cycle 

 again. As described and figured by him, the chromatin of the 

 macrogametocyte divides first into two portions, one of which is 

 smaller and stains more deeply than the other. This more 

 deeply staining portion then divides, and the protoplasm becomes 

 Segmented as in ordinary schizogony, and a young brood of 

 parasites results. The more faintly staining chromatin along 

 with part of the protoplasm breaks up and disappears. The 

 observations of Ross and Thomson, just referred to, have however 

 led them to the conclusion that the occurrence of relapses does 

 not depend on resistant forms and parthenogenesis, but on the 

 survival of asexual forms in small numbers, which pass through 

 the ordinary cycle and only produce fever when they again 

 become sufficiently numerous. 



The Sexual Cycle in the Mosquito — Sporogony. — As already 

 explained, this starts from the gametocytes. After the blood is 

 shed, or after it is swallowed by the mosquito, two important 

 phenomena occur, namely, (a) the full development of the sexual 

 cells or gametocytes, and (b) the impregnation of the female cell 

 (Plate V., Fig. 21 m-q). If the blood from a case of malignant 

 infection be examined in a moist chamber, preferably on a warm 

 stage, under the microscope, both male and female gametocytes 

 may be seen to become oval and afterwards rounded in shape 

 (Figs. 183-185). Thereafter, in the case of the male cell, a 

 vibratile or dancing movement of the pigment granules can be 

 seen in the interior, and soon several flagella-like structures shoot 

 out from the periphery (Fig. 186). They are of considerable 

 length but of great fineness, 1 and often show a somewhat bulbous 



