1902.] Terminology for the Stages of the Malaria Parasite. 77 



of the organism and its division into numerous reproductive spores. 

 Unfortunately, the word " sporocyst " has been employed recently by 

 writers on the Sporozoa for the small capsules containing one or two to 

 eight elongated spores which used to be called " pseudonaviculse," 

 and are formed within such larger cysts as that now in question. The 

 word " cyst " should have been reserved for the larger more general 

 protective envelope, and the " pseudonaviculss " might have been 

 called " sporo-thekses." In any case, I think we may call the cysts in 

 which the vermicules of the malaria parasite enclose themselves 

 "spore-cysts" or "spore-forming cysts." The name "oocyst," 

 applied to them by some writers, is simply misleading. 



7. The spore-cysts lying outside the stomach wall of the mosquito 

 bathed in the insect's blood receive abundant nourishment. The single- 

 celled vermicule enclosed undergoes rapid changes ; it increases greatly 

 in volume and breaks up by normal cell division (1 the earliest steps 

 have yet to be studied) into a number of spore-mother-cells. In the 

 process of this division and the later stages of the final development 

 of the " spores " (exotospores), the " spore-forming cyst " increases in 

 size to twenty times its initial diameter. 



The spore-mother-cells are set closely together in the cyst ; they are 

 of polygonal shape, owing to pressure, and each has its nucleus. 

 Finally they give rise, each spore-mother-cell, to a crop of filiform 

 spores (exotospores) which have the same relation to the spore-mother- 

 cell as spermatozoa have to a sperm-mother-cell, viz., they form on 

 the outside of the spore-mother-cell as outstanding processes, carrying 

 away all the chromatin of the mother-cell and leaving in the centre 

 or to one side a " residuary body," a " spore blastophore " similar to 

 the " sperm-blastophore " of spermatozoon-development. 



Thus we are brought back to the needle-like exotospores with which 

 we started. 



The spore-holding cysts burst and liberate the exotospores into the 

 blood of the mosquito. Thence they readily pass into the ducts of 

 the salivary gland, and so are conveyed by the mosquito's stabbing beak 

 into human beings. A point in this connection is the definite ejection 

 by the mosquito of the secretion of its salivary gland into the punc- 

 tured wound which it makes in the human skin. There can be no 

 doubt that such an ejection takes place. The leech ejects a secretion 

 on to the wound caused by its bite which has the property of prevent- 

 ing the coagulation of the blood. It is possible that the mosquito and 

 other blood-sucking flies may use the salivary secretion for the same 

 purpose. It is obvious that unless there were some injection into the 

 wound on the part of the fly, the chances of infection of the bitten 

 animal by the parasites carried by mosquitoes or tzetze fly would be 

 very small. 



Our cycle of forms with the names here made use of may be 



