THE hj:moflagellates. 261 



cases, however, the smaller nucleus is in contact with, or 

 attached by a delicate thread to, the larger one. 



The parasites multiply in two Avays — (a) by binary fission, 

 and (b) by multiple division or segmentation. The principal 

 stages in the first mode are well known — at least, their 

 general outlines — and certainly offer strong resemblances to 

 the process in Piroplasma. In the pyriform parasites the 

 division is evidently longitudinal (fig. 37 Ih), and, all things 

 considered, it is most probable that binary fission usually 

 takes place in the long axis (compare the figures of Rogers, 

 Laveran and Mesnil, and Donovan), the apparently transverse 

 division of oval forms being due to their being seen more or 

 less end-on. The large nucleus becomes bilobed and finally 

 constricted into two ; the smaller nucleus becomes elongated 

 transversely, and also cut into two halves ; lastly, the cyto- 

 plasm splits up, the cleavage furrow commencing either, 

 usually, at the broad or basal end, or, occasionally, at the 

 narrow, pointed extremity. Daughter-individuals, which 

 have evidently just separated, are seen lying side by side in 

 the figure. 



The other form of multiplication — multiple division — is 

 probably largely responsible for the numbers of parasites 

 with which the host-cells are often packed and distended. 

 This process, however, has not yet been so satisfactorily 

 made out as that of binary fission. It appears to conform 

 more or less to the radial or rosette type, enlarged, rounded 

 parasites, with a varying number of nuclei (up to about 

 eight), equally arranged near the periphery, having been 

 frequently'- noticed (fig. 37 If). Different writers, however, 

 describe and figure this nuclear division somewhat differently. 

 While, according to Laveran and Mesnil and Donovan, the 

 nuclei are all of one size (the two kinds of nuclear element 

 having apparently united), according to Christophers and 



as would be the case if it were rigidly limited by a spore membrane ; 

 delicate, endocellular parasites are usually capable of change in form to a 

 certain extent, and the rod-like or bacillary form well instances such a 

 change here. Compare also other Hsemosporidia. 



