368 



TR YPA NO SO MID m 



parasite elongates, and the posterior end is drawn out along the flagellum ; the 

 length is now 15 to 45 ^ and the breadth 2 to 4 ^. They are often found 

 agglomerated together. 



Longitudinal division now takes place rapidly, and the parasites pass down 

 the intestinal tract and shorten, until they become round bodies with long 

 flagella. A change then takes place, the flagellum becoming absorbed and 



Fig. 85. — The Life-Cycle of Criihidia gerridis Patton. 

 (This is a diagram constructed from Patton's drawings.) 



14, Crithidial form; 15, very slender forms; 16-18, rounded forms losing 

 their flagella; 19-3, preflagellate round forms, gradually increasing in size; 

 4, 5, formation of the flagellum; 6-8, division; 10, agglomeration; 11-13, 

 division. 



finally detached, and the parasite appearing as a rounded body with a tropho- 

 and a kineto-nucleus. The life-history is completed by the bodies being 

 discharged with the faeces into the water, and so taken up by a new host. 

 The ovaries and eggs were not infected. This is an excellent example of 

 Minchin's contaminative method of infection. 



Miss Porter has fully traced out the life-history of C. gerridis found in Gerris 

 paludum in England, and confirms Patton's researches. 



