382 RESEARCH IN PROTOZOOLOGY 



proposed the name Protcosoma grassii for the single species he 

 recognized, the fact that there was but a single species of avian 

 Plasmodium has been generally accepted. It has been evident for 

 some time, however, that there are at least several distinct varieties 

 of malarial parasites in birds, and in 1927 Hartman published a 

 paper proposing that three distinct species be recognized on the 

 basis of morphological differences. For these species, two of which 

 he regarded as new, he proposed the following names : Plasmodium 

 prcccox, Plasmodium cathemcrium, and Plasmodium inconstans. 

 Plasjuodium prcccox he believed to be identical with an avian para- 

 site described by Grassi and Feletti in 1890 under the name of 

 Hcemamcuba prcccox, and therefore retained the same specific desig- 

 nation, although these two authors evidently regarded their para- 

 site as the same as Plasmodium falciparum of man. These three 

 species differ from one another chiefly in respect to their gameto- 

 cytes (see Fig. 25), but there are also clear-cut differences in the 

 type of infection which they produce in canaries, and in the length 

 of their asexual cycles. 



2. Asexual cycles. In the case of Plasuiodlum cathemcrium the 

 length of the asexual cycle is twenty- four hours, and sporulation 

 occurs in the early evening, reaching its maximum about 6:00 p.m. 

 The length of the asexual cycle in Plasmodium inconstans has not 

 as yet been accurately determined, but is longer than that of 

 catJiemeriinn, and apparently less definite. There is also some doubt 

 as to length of the cycle in Plasinodium prcccox, although Hartman 

 (1927) states that he believes it to be the same as in catheincrium. 

 Taliaferro (1925) who first determined the length of the cycle 

 in the latter species also worked with the so-called "Whitmore 

 strain" (see below) and found the length of the asexual cycle of 

 this strain to be thirty hours. 



3. Morphology. The morphological differences are shown in the 

 accompanying figures. It will be noticed that the gametocyte of 

 Plasmodium prcccox is an elongate, rather crescent-shaped affair, 

 and that it does not displace the nucleus of the host cell. The 

 gametocytes of Plasmodium cathemcrium and Plasmodium incon- 

 stans are both of a round or somewhat irregular shape, and pre- 

 sent no conspicuous specific characters, but the pigment granules 

 of cathcmerium are much coarser and somewhat rod-like, whereas 

 those of inconstans are often nearly spherical, and very fine. In 

 both cases the nucleus of the host cell is displaced and not infre- 



