CRITHIDIA 



367 



often found this species in Ceylon, The parts of the plants affected are 

 not healthy, and the disease is called ' flagellosis.' Miss Robertson has found 

 a similar parasite in cotton plants in Uganda, It measures iO'5-i6-5X i*5 

 microns. 



Other Species. — H. gracilis Leger, 1902, in the Malpighian tubules of the 

 larvae of Tanypus ; H. lesnei Leger, 1903, in the mid-gut, near the Malpighian 

 tubules of Dasyphom pratorum ; H. subulata Leger, 1903, in the gut of Tabanus 

 glaucopis and Hcsmatopota italica Meigen; H. sarcophagcB 'Provfa.zek, 1904, in 

 the gut of Sarcophaga hcsynorrhoidalis ; H. homhycis Levaditi, 1905; H. vespcB 

 Porter, 191 1, in the gut of Vespa cvahro ; H. ctenophthalmi Mackinnon, 1909, 

 in Ctenophthalmus argyrtes ; H. drosopMlcB Chatton and Alilaire, 1908, in 

 Drosophila confusa. 



Genus Crithidia Leger, 1902, emendavit Patton, 19Q7, 



Definition. — Herpetomoninae, in which the schizo.nt is characterized by an 

 attenuated posterior end, to which the flagellum is attached by a rudimentary 

 undulating membrane. The kinetonucleus is situated close to the tropho- 

 nucleus, either on the flagellar sides or slightly and rarely a little on the 

 afiagellar aspect of this structure. 



Fig. 84. — Diagram of a Crithidia. 



Remarks. — In 1902 Leger created this genus for a flagellate organism which 

 he found in the alimentary canal oi Anopheles maculipennis , and in 1907 Patton 

 worked out the life-history of Crithidia gerridis. 



Crithidia gerridis Patton, 1908. 



This flagellate is a parasite in Gerris fossarum Fabrioius and in a species of 

 Micro velia, and in a water-bug allied to Perillopus found in Madras, The 

 flagellate is found in the crop of the insect as a round, oval, or pear-shaped 

 body, 4 to 6 ^ in length and 3 to 4 in breadth, in which lie a circular tropho- 

 nucleus and a rod-shaped kinetonucleus. 



The parasite grows and becomes vacuolated, showing, when coloured, a 

 small pink staining area between the kinetonucleus and the periphery, which 

 later becomes a distinct pink rod, and is a rudimentary flagellum attached by a 

 rudimentary undulating membrane to the cell. This membrane shows as a 

 faint pink band between the flagellum and the body of the parasite. 



Later the flagellum can be seen arising from an achromatic area, the blepharo- 

 plast, close to the kinetonucleus, and running along the periphery of the para- 

 site. 



The kinetonucleus increases in size, and the trophonucleus shows its chromo- 

 somes, while chromatic particles appear in the cytoplasm. 



The kinetonucleus now approaches the trophonucleus, and elongates and 

 divides, while the flagellum thickens and splits longitudinally, so that there 

 are two kineto nuclei and two flagella. 



The trophonucleus and the cytoplasm now divide, so that two daughter 

 cells are formed, which in turn divide, forming rosettes of eight to forty or 

 more cells, measuring 6 to 10 in length by 4 to 8 ^ in breadth. 



Eventually the rosettes break up, and the rounded parasite has a central 

 nucleus and a kinetonucleus at one side, and from a point close to this a flagel- 

 lum passes round its circumference, giving it an undulating contour. The 



