XXIII] LIFE-CYCLE 383 



The ookinetes may be observed in the gut of Lynchia within 

 three hours after a meal of infected blood. Each ookinete is 

 an elongate, somewhat gregarine-like body, that moves about 

 by means of undulations of its body. The pigment granules, 

 that originally are scattered throughout the whole of its 

 cytoplasm, become concentrated in a clump at the posterior 

 extremity (Fig. 87, p-//), which eventually is separated from the 

 rest of the body. In this manner the ookinete gets rid of the 

 waste granules in its cytoplasm. The subsequent history of 

 this form is not certain, but in all probability it does not undergo 

 any further development in the invertebrate host. When an 

 infected Lynchia bites a pigeon, the ookinetes present in the 

 front part of the insect's alimentary canal, are introduced 

 into the blood of the bird and undergo further development in 

 the leucocytes. The cycle within the vertebrate host is then 

 repeated, the parasite multiplying in the leucocytes of the 

 pigeon in the manner described above. 



It will be noticed that H&moproteus columbce possesses only 

 one method of multiplication, there being no distinct schizo- 

 gonic and sporogonic cycles as in the case of Plasmodium. 

 The parasite is apparently unable to multiply within the body 

 of its invertebrate host, Lynchia, all multiplication taking 

 place in the vertebrate host. 



H . columbce is not hereditarily transmitted to the offspring of 

 infected Lynchia, for large numbers of freshly-hatched insects 

 may be fed on a healthy pigeon without producing any infection. 



The number of halteridia appearing in the blood circu- 

 lation of a pigeon is directly proportional to the number of 

 infected Lynchia that feed on the bird. The bite of only one 

 insect produces a very mild infection, whereas when 50 are fed 

 on a pigeon, almost every corpuscle becomes infected. 



REFERENCES. 

 Aragao (1908). Der Entwicklungsgang und die Ubertragung von 



H&moproteus columbce. Arch. f. Protistenkunde , vol. xn. p. 154. 

 Mayer, M. (1910). Die Entwicklung von Halteridium. Arch. f. Schiffs. 



u. Tropenhyg. vol. xiv. p. 197. 

 (1911). Ein Halteridium und Leucocytozoon des Waldkauzes. 



Arch.f. Protistenkunde, vol. xxi. p. 232. 

 Sergent, Ed. and Et. (1907). Les Hematozoaires d'Oiseaux. Ann. 



Inst. Pasteur, vol. xxi. p. 251. 



