THE SPOROZOA 265 



order to avoid confusion between the name of the order and that of the 

 first of the two sub-orders. 



The majority of writers upon the Haemosporidia are content simply 

 to enumerate the various genera comprised in this order, without group- 

 ing them into families. Recently, however, Neveu-Lemaire has recognised 

 four families, without defining them, to include a certain number, but 

 not all, of the known genera of Haemosporidia. These are (1) the 

 family Haemogregarinidae, equivalent in extent to the whole sub -order 

 Haemosporidia sensu stricto, and comprising the genera Lankesterella 

 ( = Drepanidium), Karyolysus, and Haemogregarina ; (2) family Haem- 

 amoebidae (Wasielewski), comprising the genera Plasmodium, Laverania, 

 and Haemamoeba ( = Haemoproteus s. Proteosoma) ; (3) family Halterididae 

 for Halteridium and Polychromophilus ; (4) family Achromaticidae for Achro- 

 maticus and Dactylosoma (synonym of Drepanidium). Amongst the genera 

 left out in the cold is Piroplasma ( = Apiosoma), a genus which is 

 sufficiently well characterised to be the type of another family ; while on 

 the other hand the position and importance of the genera Polychromo- 

 philus and Achromaticus must remain for the present doubtful. The 

 arrangement of the genera in families seems, therefore, rather premature 

 in the present state of knowledge. 



With regard to number of generic types to be recognised amongst 

 the Haemosporidia, the greatest diversity of opinion prevails. Laveran 

 [75, 77], to whose authority, as the original discoverer of .the malarial 

 parasites, the greatest weight attaches, recognises but three genera : 



(1) Haemamoeba [including Plasmodium, Laverania, Haemoproteus, etc.] ; 



(2) Piroplasma; and (3) Haemogregarina [including Drepanidium and 

 Karyolysus]. This classification has at least the merit of simplicity, 

 but in lumping the genera together to such an extent, Laveran is not 

 followed by other writers, and his three genera are to be regarded rather 

 as representing groups of the value of families in a natural system. 



In the following systematic review, the genera best characterised and 

 commonly recognised are given first, and then a certain number of 

 doubtful forms are briefly mentioned. 



ORDER Haemosporidia, Danilewsky. 

 SUB-ORDER I. HAEMOSPOREA. 



Trophozoite typically a vermiform haemogregarine, endoglobular in 

 early stages, free when full grown. Apparently no alternation of hosts ; 

 schizogony and sporogony in the same host, which is always a cold-blooded 

 vertebrate, fish, amphibian, or reptile. 



Genus 1. Lankesterella, Labbe", 1899 (for Drepanidium, Lankester, 

 1882), preoccupied. The haemogregarine is not more than three-fourths 

 the length of the blood-corpuscle it inhabits. Type-species L. ranarum, 1 

 Lankester (Fig. 75), parasitic on Rana esculenta; L. monilis (Labbe"), from 



1 According to Hintze [68], this form was first described by Chaussat in 1850 

 under the name of Anguillula minima, so that its correct designation would be 

 Lankesterella minima (Chaussat). 



