Enteritis in Native Animals. 435 



zone rest, uniform in thickness and staining deeply. The exter- 

 nal " fringe " is fairly uniform in breadth, averaging 20 /x in 

 the younger stages (Plate LXXIV., Fig. 2), but in the older stages 

 it is extremely irregular, especially at certain situations where 

 it sends out long branching and anastomosing processes into 

 the surrounding tissue, and is invaded by polymorphs (Plate 

 LXXIV., Fig. 6), of which, immediately around nearly all cysts, 

 there is a distinct accumulation. 



The contents consist of a homogeneous endoplasm, uniformly 

 staining, but for faint concentric striations probably due to con- 

 traction in fixing. Towards the centre of this endoplasm are 

 situated numerous blastophores, more or less spherical areas 

 without a limiting membrane containing nuclei, which gradually 

 develop into mature spores. The younger the parasite the 

 greater is the amount of endoplasm present, and in the earliest 

 stages observed it not only distinctly separates each blastophore 

 from its neighbour, but more completely separates the most 

 peripheral of the blastophores from its envelope. As the cyst 

 develops, however, the endoplasm becomes reduced, ultimately 

 the blastophores generally, though not always, lying close 

 together, and immediately underneath the inner zone of the 

 envelope (Plate LXXV., Fig. 7). Both the envelope and the endo- 

 plasm stain definitely with eosin, and such acidophile dyes. 



The blastophores within the endoplasm vary considerably 

 in number, the average being from 60' to 80 in a median section. 

 What may be described as three distinct stages are observed. 

 In the youngest cysts (measuring from 0.0134 mm. to 0.0335 

 mm. in diameter) they are irregularly but more or less centrally 

 grouped. The nuclei, which vary from 7 to 20, are peripherally 

 arranged, and lie in a fine granular basophile material. The 

 second stage shows an increase both in size (0.225 to 0.0584 mm.) 

 and in the number of nuclei, the granular material being sepa- 

 rated into masses around which the nuclei are arranged. These 

 masses seem to divide as the nuclei further increase and ulti- 

 mately each blastophore is crowded with nuclei still arranged 

 mulberry-like around small portions of the granular material. 

 In the third stage (0.0334 to 0.075 mm.) of the development, the 

 nuclei are seen to develop small peripheral cones of finely 

 granular protoplasm ; gradually the central mass divides until 



