438 J. A. GilriUh and L. B. Bull 



Large Cysts. Ileoeystis macropodis. 



TTiese may be found singly, but generally in groups or clusters 

 of three to eight (Plate LXXVI., Figs. 2 and 10). At times irre- 

 gular in size, they are generally fairly uniform, when the appear- 

 ance is that of a circular mass divided distinctly into three or 

 more triangular segments, each with a crescentic base. These 

 groups vary in size from 0.07 to 0.334 mm. in diameter. Like 

 the wallaby cysts, each is provided with an envelope and with a 

 homogeneous endoplasm within which is situated one blasto- 

 phore (or perhaps schizont). The envelope shows at the free 

 edge a fringe-like external coat, of an average breadth of 8/a, 

 the striations being much finer and more regular than in the 

 wallaby cysts. There is a definite thin inner coat, staining 

 faintly blue with haematoxylin and eosin, and brownish with 

 Van Gieson, while the bases of the fringe form at their junction 

 a faintly staining intermediate zone, into which the striations 

 are seen to prolong. The fringe and the endoplasm are acido- 

 phile, the former staining the less deeply. Where two cysts 

 approximate the fringe is lost, but the faintly staining inter- 

 mediate zone can be seen to extend between the two adjacent 

 cysts, separating the endoplasm of the one from the other, and 

 varying in breadth in the different groups (Plate LXXVIIL, 

 Pig. 12). 



Within the endoplasm, lying almost invariably next the cres- 

 centic free border, lies always (as can be seen in serial sections) 

 a large granular deeply staining body, which varies in shape : in 

 the smaller cysts it is irregularly spherical, and exceeds in size 

 the blastophore, in the larger cysts it is in the form of a long 

 triangle or narrow long spindle (Plate LXXVL, Figs. 9 and 10). 

 This body is probably the hypertrophied nucleus of the original 

 cell, and indeed what appear to be the large spherical nucleoli 

 can often be detected among the deeply staining granular 

 material. These nuclei vary in size greatly, being in the younger 

 cysts 14.6/x in diameter, and in the oldest from 79.2/^ to 

 95.9/M long, and 8.34/x to 18.7/x broad. At first we were 

 inclined to the opinion that these peripheral deeply staining 

 masses were degenerated blastophores similar to those seen in 



