Genus Laverania, Gr. and Fel. (syn. Haemamoenas, Ross), for L. malariae, Gr. and Fel. (synn. L. s. Plasmodium, s. “Haemamoeba,” &c., praecox s. immaculatum, &c.), the parasite of pernicious malaria. Genus Plasmodium, March. and Celli (syn. “Haemamoeba”) for P. vivax and P. malariae, the tertian and quartan parasite, respectively. There is also a form known in apes, P. kochi. Genus Haemoproteus, Kruse (syn. Proteosoma), for H. danilewskyi (syn. Proteosoma grassi, Plasmodium praecox, &c.), parasitic in numerous birds. Recently, another form has been described, from reptiles, which Castellani and Willey have termed Haemocystidium simondi.
Remarks.—The distinguishing characters of the malarial parasites have been mentioned above. Some authorities would include Laverania in the genus Plasmodium, as differing only specifically from the other two forms. It has, moreover, been suggested by Sergent that all three are merely different phases of the same parasite, predominating at different seasons; this idea cannot be regarded, however, as in any way proved so far. From what is known of the morphology and mode of manifestation of these forms, the differences between Laverania and the two species of Plasmodium are considerably more pronounced than those between P. vivax and P. malariae; if the latter are to be considered as distinct species, the first-named is probably generically distinct. Lühe, it may be noted, in his recent comprehensive account of the Haematozoa, also takes this view. Lastly, whatever be the correct solution of the above problem, there is certainly not sufficient justification for including the Avian genus Haemoproteus, as also only a species of Plasmodium, which is done by some. Its different Vertebrate habitat, and also the fact that its Insectan definitive host is Culex and not Anopheles, differentiate it sharply from Laverania and Plasmodium.
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| From Lankester’s Treatise on Zoology. | |
| Fig. 5.—Haemoproteus danilewskyi, Kruse (parasite of various birds). × about1200. a, b, c and d from the chaffinch; d and e from the lark. (After Labbé.) | |
a, Young trophozoite in a blood-corpuscle, b and c, Older trophozoite. d and e, Sporulation. d, Precocious sporulation with few merozoites. e, Sporulation of a full-grown schizont, with numerous merozoites. f, Gametocyte. | N, Nucleus of blood-corpuscle. n, Nucleus of parasite. p, Pigment. mz, Merozoites. r.p, Residual protoplasm. |
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| From Lankester’s Treatise on Zoology. | |
| Fig. 6.—Haemogregarina stepanovi, Danilewsky (par. Emys andCistudo), phases of the schizogony. (a-e and j after Laveran; f-iafter Börner.) × 1000 to 1200 diameters. | |
a, Blood-corpuscle with youngtrophozoite. b, Older trophozoite. c, Full-grown trophozoite, readyto leave the corpuscle. d and e, Trophozoites free in theblood-plasma, showingchanges of form. f-i, Trophozoites, still within theblood-corpuscle (not drawn),showing the structure of thenucleus, the coarse chromatoidgranules in the protoplasmand the manner inwhich the parasite growsinto the U-shaped Haemogregarinewithout increase ofbody-mass. | j, Commencement of sporulation;the nucleus has dividedinto eight nuclei, and thebody of the parasite isbeginning to divide up intoas many merozoites within ablood-corpuscle. N, Nucleus of the blood-corpuscle. n, Nucleus of the parasite. |
Fam. Haemogregarinidae.—The different genera are characterized chiefly by their size relative to the blood-corpuscles, and their disposition in the latter. Here, again, it has been suggested to unite the various types all in one genus, Haemogregarina, but this seems at least premature when it is remembered how little is known in most cases of the life-cycle, which may prove to exhibit important divergences.
Genus Haemogregarina, Danilewsky (syn. Danilewskya, Labbé). The body of the parasite exceeds the blood-corpuscle in length, when adult, and is bent upon itself, like a U. A very great number of species are known, mostly from reptiles and fishes; among them may be mentioned H. stepanovi (fig. 6), from Emys and Cistudo, whose sexual-cycle in a leech has been worked out by Siegel (see above), H. delagei, from Raja, H. bigemina, from blennies, and H. simondi, from soles. Recently one or two Mammalian forms have been observed, H. gerbilli, from an Indian rat (Gerbillus), and H. jaculi, from the jerboa.
Genus Lankesterella, Labbé (syn. Drepanidium, Lankester). The parasite is not more than three-quarters the length of the corpuscle. L. ranarum from Rana is the type-species; another, recently described by Fantham, is L. tritonis, from the newt.
| From Lankester’s Treatise on Zoology. |
| Fig. 7.—Karyolysus lacertarum (Danil.), in the blood-corpuscles of Lacerta muralis, showing the effects of the parasite upon the nucleus of the corpuscle. In c and d the nucleus is broken up. N, Nucleus of the corpuscle; n, nucleus of the parasite, seen as a number of masses of chromatin, not enclosed by a distinct membrane. (After Marceau.) |
Genus Karyolysus, Labbé. The parasite does not exceed the corpuscle in length; the forms included in this genus, moreover, although not actually intranuclear, have a marked karyolytic and disintegrating action upon the nucleus of the corpuscle. The type-species is the well-known K. lacertarum, of lizards; another is K. (Haemogregarina) viperini, from Tropidonotus.
In the section of the Piroplasmata there is only the genus Piroplasma, Patton (synn. Babesia, Starcovici, Pyrosoma, Smith and Kilborne), the principal species of which are as follows: P. bigeminum, the cause of Texas cattle-fever, tick-fever (Rinder-malaria) of South Africa, and P. bovis, causing haemoglobinuria of cattle in Southern Europe; there is some uncertainty as to whether these two are really distinct; P. canis, P. ovis and P. equi associated, respectively, with those animals. Lately, a very small form, P. parvum, has been described by Theiler in Rhodesia, which causes East-African coast-fever; and another, P. muris, has been observed in white rats by Fantham.