H^MOSPORIDIA 151 



Order. Haemosporidia, Danilewsky emend. Schaudinn. 



The Haemosporidia are a group of blood parasites, comprising 

 forms differing greatly among themselves. Some of the forms need 

 much further investigation. However, there are certain true Haemo- 

 sporidia which present close affinities with the Coccidia, leading 

 Doflein to use the term Coccidiomorpha for the two orders conjoined. 



The Haemosporidia present the following general characteristics : 



(1) They are parasites of either red or white blood corpuscles of 

 vertebrates during one period of their life-history. 



(2) They exhibit alternation of generations asexual phases or 

 schizogony alternating with sexual phases or sporogony as do the 

 Coccidia. 



(3) There is also an alternation of hosts in those cases which have 

 so far been completely investigated. The schizogony occurs in the 

 blood or internal organs of some vertebrate while the sporogony 

 occurs in an invertebrate, such as a blood-sucking arthropod or leech. 



(4) Unlike the Coccidia, resistant spores in sporocysts are not 

 generally produced, such protective phases in the life-cycle being 

 unnecessary, as the Haemosporidia are contained within either the 

 vertebrate or invertebrate host during the whole of their life. 



The Haemosporidia may be considered for convenience under 

 five main types : 



(1) The Plasmodiinn or Hcemamceba type. This includes the 

 malarial parasites of man and of birds. The asexual multiplicative 

 or schizogonic phases occur inside red blood corpuscles and are 

 amoeboid. They produce distinctive, darkish pigment termed melanin 

 or haemozoin. Infected blood drawn and cooled on a slide may 

 exhibit " exflagellation " of the male gametocytes, i.e. t the formation 

 of filamentous male gametes. The invertebrate host is a mosquito. 

 The malarial parasites of man are discussed at length on p. 155. 

 Similar pigmented haemamceboid parasites have been described in 

 antelopes, dogs, and other mammals, and even reptiles. 



(2) The Holier idium type. The trophozoite stage inside the red 

 blood corpuscle is halter-shaped. Pigment is produced, especially near 

 the ends of the organism. The parasites occur in the blood of birds. 

 The invertebrate host of H. coliunbce of pigeons in Europe, Africa, 

 Brazil and India, is a hippoboscid fly, belonging to the genus Lynchia. 



Halteridium parasites are common in the blood of passerine birds r 

 such as pigeons, finches, stone owls, Java sparrows, parrots, etc. 

 The Halteridium embraces or grows around the nucleus of the host 

 red cell without displacing the nucleus. Young forms and multipli- 

 cative stages of H. columbce have been found in leucocytes in the 

 lungs of the pigeon (fig. 76, 8-12). Male and female forms (gameto- 

 cytes) are seen in the blood (fig. 76, jn, jb). The cytoplasm of the 



