480 TELOSPORIDIA " 



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not merely traced out the cycle of schizogony, but also fully that of sporogony. 

 This was the first description of the full life-history of a hsemogregarine ever 

 given. This paper is also of the greatest importance in arranging the classifi- 

 cation of the Haemogregarinida, for, as already stated, Ray Lankester in 1871 

 believed that H. minima might be a stage of Trypanosoma rotatorium, and in 

 this was supported by Billet in 1904, who considered that he could infect 

 clean frogs with haemogregarines by the bites of leeches containing trypano- 

 somes. 



Brumpt's experiments in 1904 on the sporogony of H. bagenesis in the leech 

 {Placobdella catenigera) also supports this theory by finding a binucleate 

 condition in the ookinetes. Miss Robertson believes that haemogregarines have 

 a trypanosoma stage. These observers would therefore classify the Haemo- 

 gregarinida with the Binucleata; but against this Brumpt in 1907 has shown 

 that Billet was probably mistaken, for if leeches infected with T. inopinatum 

 are placed on a ' clean ' frog a trypanosomiasis results, and the fact that 

 though Sambon has often seen haemogregarines in snakes and lizards, trypano- 

 somes are absent or rare. 



The life-history of H. muris as worked out by Miller shows no trypanosome 

 stage, and clearly indicates that the Haemogregarinida belong to the Telo- 

 sporidia, and are related to the Gregarinida and Coccidiidea, as was pointed 

 out by Laveran in 1898. 



"With regard to the Haemogregarinida of reptiles, a very complete work 

 is that of Sambon in 1908 on the parasites in snakes, where a full history 

 will be found. Those which occur in tortoises and crocodiles have been 

 studied by Danilewsky, Castellani and Willey, Miss Robertson, Dobell, and 

 others, while Siegel has worked out fully the schizogony and sporogony of 

 H. stepanovi in the leech. 



The Haemogregarinida of lizards have been studied by Danilewsky, Laveran, 

 Minchin, C. Fran9a, and others, and those of amphibia by Chaussat, Lankester, 

 Billet, Durham, I3rumpt, Labbe, Lesage, and others. 



Life-History. — The most accurately known life-history is that given for 

 H. muris Balfour by Miller. 



Schizogony. — The asexual reproduction takes place in the cells of the liver> 

 in which the young trophozoite appears as a small spherical organism with a 

 large vesicular nucleus containing a well-defined karyosome. The trophozoite 

 grows at the expense of the liver cell, the nucleus of which is pushed to one 

 side, and in due course becomes a schizont, which divides into twelve to twenty 

 merozoites, and a ' rest ' body. 



Some of these merozoites on liberation enter fresh liver cells, and continue 

 the cycle of schizogony, while others enter mononuclear leucocytes, in which 

 they become encysted, and develop into gametocytes. 



Sporogony. — Sexual reproduction takes place in a mite belonging to the 

 Gamasidae called Lelaps echidninus Berlese, which lives on the blood of the rat. 



The gametocytes, liberated from the leucocytes by the digestive action of 

 the juices of the mite's gut, arrange themselves in couples, which are at first 

 exactly similar, but which later differentiate into a large encircling form, 

 which is more granular, and which is probably the macrogamete, and a smaller, 

 more rounded, and less granular microgamete. Zygosis now takes place, 

 forming an ookinete, which grows, and leaving the gut by piercing the wall, 

 forces its way into the body cavity, which consists of a series of small spaces 

 between the organs, and further into the sheaths of the muscles, and into the 

 investing membrane of the salivary glands. 



In the tissues the ookinete encysts and becomes the oocyst, which grows 

 rapidly in size, and undergoes nuclear division. 



The daughter nuclei migrate to the periphery, which becomes covered with 

 50 to 100 bud -like projections, in each of which a nucleus is to be found. These 

 buds break off from the central mass, and form the sporoblasts, the nuclei of 

 which divide, forming daughter nuclei, which gather at the poles, while the 

 whole sporoblast encysts. Short rod-like processes of cytoplasm, each con- 

 taining a nucleus, now break off from the sporoblasts, each of which becomes 

 a sporozoite, of which there are on an average sixteen to each sporoblast. 



