THE H^MOSPORIDIA 373 



corpuscle, instead of a red, does not of itself supply adequate grounds for a 

 generic, or even for a specific, distinction, since in some species for example, 

 H. agamce the parasites may occur either in white or red corpuscles (Laveran 

 and Pettit). For the present, therefore, these leucocytozoa, so called, may 

 remain in the genus Hcemogregarina, until greater knowledge of the life-histories 

 of haemogregarines makes possible a natural classification of these organisms. 

 A hsemogregarine of leucocytic habitat has been described also from a frog 

 by Carini (Rev. Soc. Sci., Sao Paulo, 1907, p. 121). 



As a type of the life-cycle of the haemogregarines may be taken 

 H. stepanowi (Fig. 159), which has been studied by Reichenow (78). 

 The chief points in this author's account of the life-history are con- 

 firmed in essential details, but with specific variations, by that 

 given by Robertson (725) for the life-cycle of H. nicorice* In both 

 cases the developmental cycle in the tortoise comprises two forms 

 of schizogony, the one producing schizonts, the other sporonts ; 

 and the invertebrate host is a leech. 



(1) The sporozoite penetrates into a blood-corpuscle, and grows 

 into a long vermicule, which is at first doubled on itself (Fig. 159, F). 

 The two limbs of the U-shaped body within the corpuscle fuse 

 together to produce a bean-shaped parasite the macroschizont. 



(2) The macroschizont of H. stepanowi, remaining within the 

 blood-corpuscle, goes through its schizogony in the bone-marrow 

 of the tortoise, producing some thirteen to twenty-four macromero- 

 zoites (Fig. 159, B, C}. The number produced is larger in the earlier 

 stages of the infection than in older infections (Fig. 159, D H). 

 In H. nicorice, however, the macroschizont is set free in a capillary 

 of the lung, and there produces about seventy macromerozoites. 



In the account of the schizogony given by Reichenow, the significance of the 

 recurved vermicules is not clear. In drawn blood they can be observed to 

 be set free from the blood- corpuscles, and then, as free vermicules, to 

 exhibit active powers of movement, which indicate the existence of some sort 

 of locomotor apparatus, probably of myonemes. According to Reichenow, 

 however, liberation from the corpuscle never occurs normally within the 

 body of the tortoise, but the recurved vermicule remains within the blood- 

 corpuscle in which it has grown up, and its two limbs fuse to form the body 

 of the bean-shaped macroschizont. If that is so, it is difficult to understand 

 why the motile vermicule is ever developed. One is inclined to suspect that 

 it becomes free from the .corpuscle in which it has developed, and as a " schizo- 

 kinete " (Minchin and Woodcock, 483) finds it way as a motile vermicule 

 to the bone -marrow (or lung in H. nicorice), where it penetrates another 

 corpuscle (or remains free in a capillary vessel, H. nicorice) and becomes the 

 macroschizont. 



(3) The macromerozoites produced penetrate into blood-cor- 

 puscles, and may (a) repeat the development already described, and 

 become macroschizonts again ; or they may (b) develop into micro- 

 schizonts, which produce micromerozoites in small numbers, 



* Nothing in the work of these authors confirms in any way the peculiar account 

 of the life-history of H. stepanowi given by Hahn, whose work is criticized by 

 Reichenow. 



