256 



THE SPOROZOA 



merozoites produced by schizogony. Within the cytocyst the 

 schizont may break up into smaller micromerozoites or larger macro- 

 merozoites. 1 This occurs in the form Karyolysus lacertarum (Fig. 73), 

 and also in the haemogregarines infesting various snakes studied 

 by Lutz [82] and named by him " Drepanidium serpentium." In 

 the latter the two kinds of merozoites develop into two forms 

 of schizonts termed by Lutz microhaemozoites and macrohae- 

 mozoites respectively. Dimorphism in the cytocysts has also been 

 described by Labbe in Lankesterella, but has not been confirmed 

 by recent observers. The most obvious interpretation of these 

 facts would seem to be that in these forms the schizonts show a 



a 



d. 



Karyolysus lacertarum, Labbe, sporulation. a, macroschizout crammed with plastinoid 

 granules (pl.y) encysted in a blood -corpuscle, forming a cytocyst. 6, later stage of the same ; 

 the schizont has grown in size, its nuclei (71) are multiplying, and the degenerated remains of 

 the corpuscle and its nucleus (D) form the outer envelope of the cytocyst. c, cytocyst con- 

 taining macromerozoites (MZ) and two residual masses of protoplasm (r.p), one at each pole. 

 The macromerozoites, distinguished by their large size, contain a few small plastinoid granules. 

 d, cytocyst containing micromerozoites (niz) and a single residual mass (r.p). N, nucleus of the 

 blood-corpuscle ; , nucleus of the parasite. (After Labbe.) x about 1000 diameters. 



precocious sexual differentiation comparable to what is seen in 

 Adelea amongst Coccidia. 



Observations upon the sexual cycles of Haemosporidia are as 

 yet few and somewhat far between, and it is necessary to be very 

 cautious in making generalisations. The parasites of birds and 

 man have been the chief objects of research, but not much is 

 known with regard to the Haemosporidia of the lower Vertebrata. 

 Eecently, however, Hintze [68] has brought forward interesting 

 observations upon Lankesterella ranarum. The microgametocytes 

 (Fig. 75, g) are distinguished by their slender form, and by the 

 absence of all but the finest granulations in their protoplasm, from 

 the plump, coarsely granular macrogametocytes (Fig. 75, j), the 

 ordinary schizonts being intermediate in character between the 

 two. In the microgametocytes the nucleus contains a number of 

 chromatin granules, each of which divides into two. The nucleus 



1 Commonly, but probably wrongly, termed microsporozoites and macrosporozoites. 



