522 APPENDIX C. 



quito, two important phenomena occur, viz., (a) the exflagellation of the 

 male gamete, and (b) the impregnation of the female. 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 gametes 

 may be seen to become oval and afterwards rounded in shape (Figs. 

 165-167). Thereafter, in the case of the male cell, a vibratile or danc- 

 ing movement of the pigment granules can be seen in the interior, and 

 soon several flagella-like structures shoot out from the periphery (Fig. 

 1 68). They are of considerable length but of great fineness, and often 

 show a somewhat bulbous extremity. By the Romanowsky method they 

 have been found to contain a delicate core of chromatin, which is covered 

 by protoplasm. They represent the male cells proper, that is, they are 

 sperm-cells or spermatozoa ; they are also known as microgametocytes. 

 They become detached from the sphere and move away in the surround- 

 ing fluid. One of them may enter a female gamete and thus a process 

 of true impregnation occurs. It is also stated that the female cell 

 before fertilisation gives off two polar bodies. This was first observed by 

 MacCallum in the case of halteridium, and he found that the female cell 

 afterwards acquired the power of independent movement or became a 

 " travelling vermicule." He also observed the impregnation of the malig- 

 nant parasite. The fertilised female cell is now generally spoken of as 

 a zygote. 



It has been established that the phenomena just described occur 

 within the stomach of the mosquito, and that the fertilised cell or zygote 

 penetrates the stomach wall and settles between the muscle fibres ; on 

 the second day after the mosquito has ingested the infected blood small 

 rounded cells about 6-8 /x in diameter and containing clumps of pigment 

 may be found in this position. (It was in fact the character of the pig- 

 ment which led Ross to believe that he had before him a stage in the 

 development of the malarial parasite.) A distinct membrane called 

 a sporocyst forms around the zygote, and on subsequent days a great 

 increase in size takes place, and the cysts come to project from the sur- 

 face of the stomach into the body cavity. The zygote divides into a 

 number of cells called blastophores or spore-mother-cells, and on the sur- 

 face of each there are formed a large number of filiform spores which 

 have a radiate arrangement ; these were called by Ross " germinal rods," 

 but are now usually known as zygotoblasts or exotospores (in contradistinc- 

 tion to the enhsemospores of the human cycle) . The full development 

 within the sporocyst occupies, in the case of proteosoma, about seven 

 days, in the case of the malarial parasites a little longer. When fully 

 developed the cyst measures about 60 p. in diameter, and appears packed 

 with zygotoblasts. It then bursts, and the latter are set free in the body 



