264 



2. Hg. gerbilli. In the red cells of Gerbillus 

 indicus, an Indian field rat. Parasites are generally 

 numerous. It is non-pathogenic. Two forms occur. 



(i) Endo globular. They lie in sharply defined oval 

 cavities limited by a 4 cytocyst,' probably derived from 

 the red cell. The parasite possesses a short tail sharply 

 flexed upon the body. In stained specimens a nucleus 

 is visible just before the bend of the tail. The tail 

 portion stains deeper than the rest of the parasite and 

 contains a number of chromatin granules. The red 

 cells are anaemic and enlarged, and become oval, 

 corresponding to the shape of the parasite. 



(ii) Vermicides. These are best seen in blood 

 that has been kept moist for some time. They 

 resemble the encysted forms except that now the tail 

 is straightened out (Fig. 79). 



3. Hg. canis. Occurring in the polynuclear 

 leucocytes of dogs, especially puppies, in India and 

 Assam. They are about 12 by 6^, and occur in 

 a capsule or cytocyst derived from the leucocyte. The 

 nucleus is generally situated at one end, and is round 

 or oval" (Fig. 80). 



Development. One of us (S. R. C.) has traced the 

 development of this parasite in the gut of Eu. san- 

 guineus, the Indian dog tick. 



(i) The parasites become free, and become vermi- 

 cular in shape. 



(ii) The vermicule enters a cell of the gut and pro- 

 ceeds to divide, giving rise to a slender and stout form. 



(iii) Conjugation of these takes place, resulting in 

 a zygote. 



(iv) These grow in size and eventually in them 

 develop sausage-shaped sporozoits. 



(v) How these get out of the tick and infect dogs 

 is unknown. 



