ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 477 



Assuming that this is true, the life-history of Sarcocystis muris 

 would be as follows : — The ingested spores gain the epithelium of the 

 intestine and develop into the macrogametes and microgametes. The 

 latter fertilize the former and produce the zygotes. By endogenous 

 multiplication the zygotes produce a number of minute elements. There 

 is here a gap in the life-history. Two divergent lines are followed, for 

 some phases appear in the freces and others in the muscles. The form 

 that invades the muscle is either the sporoblast itself or its immediate 

 forerunner, which may be the zygote or some element derived from the 

 zygote. In auy event, at a certain point in the history, the muscle cells 

 come to harbour individual sporoblasts. These divide many times by 

 bi-partition, but eventually the products of these divisions are no longer 

 sporoblasts, but spores. Unless its development be interfered with, 

 each sporoblast will presumably produce a cyst. 



This life-history is compared in detail with that of a typical member 

 of the Coccidiomorpha. The Sarcosporidian " spore " is the homologue 

 of the Coccidiomorphan merozoite. The sexual stages are alike. The 

 multiplication products of the Sarcosporidian zygote are presumably the 

 homologues of either the spores or spprozoites of the Coccidiomorpha. 

 The sporoblast is not so easy to place. It may correspond either to the 

 sporozoite or to the trophozoite of the Coccidiomorpha. The Sarcospo- 

 ridian muscle stage is comparable to the entire schizogonous cycle of 

 the Coccidiomorpha. In the latter, the products of schizogony are set 

 free and are enabled to invade new regions of the host. In the former, 

 a tissue reaction on the part of the host confines them to the region 

 originally invaded. 



If the line of reasoning indicated be sound, the Sarcosporidia are not 

 Neosporidia, but Telosporidia, and moreover Telosporidia which belong 

 to the Coccidiomorpha. The Sporozoa may be divided into two 

 sub-classes, Telosporidia and Neosporidia. In the first, division into 

 multiplicative elements takes place only at the end of the vegetative 

 period. In the second, growth and spore-formation take place simul- 

 taneously. 



The re-classification proposed reads as follows : — 



Class SPOROZOA. 



Sub-class I. Telosporidia. 



Order 1. Coccidiomorpha. 



Sub-order A. Coccidia. 



„ B. Hsemosporidia. 



„ C. Sarcosporidia. 

 Order 2. Gregarinida. 



Sub-class II. Neosi'ORidia. 



Order 1. Cnidosporidia. 



Sub-order A. Mysosporidia. 

 „ B. Microsporidia. 

 „ C. AcLinomyxidia. 

 Order 2. Haplosporidia. 



