INTRODUCTION. 9 



a large number of gametes, those from one individual fusing 

 with those from the other, and a corresponding number of 

 zygotes are formed. Within the membrane the zygotes 

 develop into spores, each dividing to form a definite number 

 of sporozoites. 



Among the Amcebosporidia (=Nbosporidia) the life-cycle 

 is less compUcated, and sexual dimorphism and change of hosts 

 are not met with. Reproduction takes place more or less 

 continuously throughout the trophic phase, the organism 

 ultimately becoming a huge mass of spores. Spore-formation is 

 also on an entirely different plan from that in the Telosporidia, 

 and does not usually result from the divisions of a zygote. 

 The life-histories among the subclasses Cnidosporidia, 

 Sarcosporidia, and Haplosporidia differ considerably, and 

 it is impossible to attempt a generahzed account : reference 

 must therefore be made to the detailed accounts given under 

 these different subclasses. Among the Cnidosporidia both 

 schizogony and sporogony are met with. Schizogony is 

 carried out by binary or multiple fission, by budding, or by the 

 cleavage of the multinucleated plasmodium into two or more 

 multmucleate parts (plasmotomy) . Isogamous, anisogamous, 

 and autogamous reproduction have been reported in a number 

 of forms, and the zygote becomes the sporont, in which 

 one to many spores become differentiated. The spores are of 

 a unique structure. Each spore possesses one to four polar 

 capsules, each containmg a coiled polar filament, and one to 

 many sporoplasms. The mode of development of these spores 

 differs in different cases. In the orders Myxosporidia and 

 AcTiNOMYXiDiA Several cells appear during the process. 

 These cells give rise to one or more sporoplasms or generative 

 cells, capsulogenous cells, and the spore-membrane. In 

 the order Microsporidia the amoeboid sporopiasm undergoes 

 schizogonic multiphcation, and the schizonts later become 

 sporonts, each producing the characteristic number of spores. 



The Sarcosporidia produce long rod-like masses of spores 

 among the muscle-fibres, which they parasitize. The spores 

 are crescentic in outhne and do not contain polar capsules. 

 Only portions of the full hfe-cycle are known. 



The Haplosporidia show a comparatively simple Hfe-cycle. 

 The spores are spherical or elhpsoidal, with a single large 

 nucleus and no polar capsule. The amoebula grows, and by the 

 repeated division of the nucleus forms a plasmodium. The 

 Plasmodium may divide (plasmotomy) or may produce mero- 

 zoites (schizogony) or form spores. The spores arise either 

 from sporoblasts, each of which gives rise to a single spore, 

 or from pansporoblasts, which give rise to a number of 

 spores. 



