270 THE PATHOGENIC HEMOSPORIDIA 



the blood stream, which conveys them to the hver (Fig. 106, a to d). 

 Here they enter the Hver cells and undergo schizogony, about 16 

 merozoites being formed. These may enter other liver cells or pass 

 into the blood stream, where they are taken up by large mononuclear 

 leukocytes in which they remain protected by a distinct membrane or 

 cyst (Fig. 106,/). If such infected blood is taken by a mite, the encysted 

 parasite is set free in the insect's digestive tract. Two similar ones con- 

 jugate in the lumen of the gut (Fig. 106, g to k) and a motile ookinete 

 penetrates the stomach wall and gets into the body cavity. In the body 

 tissues the fertilized cell rapidly increases in size, the fertihzation 

 nucleus divides a number of times, and the daughter nuclei migrate to 

 the periphery of the cell, where they lie in minute papillae on the sur- 

 face. The papilliE enlarge and grow into sporoblasts, each of which 

 ultimately gives rise to about sixteen sporozoites (Fig. 106, o, p). 

 Mature parent cysts contain from 50 to 100 of such sporocysts. 

 When such an infected mite is swallowed by a rat the sporozoites are 

 liberated and the cycle completed. 



Trypanosoma and Leishman-Donovan bodies (herpetomonas 

 donovani) are acknowledged flagellates, but babesia and a fortiori 

 Plasmodium, and other hemosporidia, stand very far removed from 

 such more primitive forms, and although there is good reason to believe 

 that hemosporidia and, through them, coccidiidia have been derived 

 from mastigophora, to classify them as such would be unwarranted. 

 The so-called "flagella" of babesia have little in common with this 

 characteristic motile organ of the flagellates, and Doflein's, Nuttall 

 and Graham-Smith's, and Kinoshita's view that they may be micro- 

 gametes, although not demonstrated in any case, seems much more 

 plausible and will remain so until the process of fertilization is fully 

 known. The method of microgamete formation in plasmodium gives 

 rise to reproductive bodies which are strikingly similar to the so-called 

 flagella of Babesia canis, as described by Bowhill and Le Doux ('04), 

 Nuttall and Graham-Smith ('04- '07), and especially by Breinl and 

 Hindle ('08), who find two "flagella" appearing successively. The 

 long history of the "polymitus" form of plasmodium should be a 

 warning against premature conclusions regarding these structures. 

 The process of sporulation in plasmodium and in Babesia canis, 

 according to Christophers ('04), in the bodies of the invertebrate hosts 

 is entirely different from reproduction in pathogenic flagellates, while 

 save for the absence of spore cases, it conforms exactly with the sporo- 

 zoan type. For these reasons, therefore, I believe it premature to 

 separate the hemosporidia from sporozoa, but recognize the phylo- 

 genetic possibilities indicated by such a series as herpetomonas, 

 crithidia, trypanosoma, babesia, hemoproteus, and plasmodium. 



A. The Genus Babesia.— Smith and Kilborne ('93) found 

 peculiar minute parasites in the red blood corpuscles of cattle sick 



