INTRODUCTION. 3 



(1923-5) designated the two classes as Sporozoa and 

 Amcebosporidia, and something can be said in favour of 

 this system of classification. Wenyon (1926) also divided 

 the entire group into two classes, and named them as 

 Sporozoa and Cnidosporidia, leaving the Sarcosporidia and 

 Haplosporidia as parasites of undetermined position. 

 Theoretically speaking, there is no difficulty in restricting 

 the term Sporozoa to the original connotation which Leuckart 

 gave it, but in practice it would seem impossible so to restrict 

 it, unless a new term like Sporogbnea is coined for a sub- 

 phylum to include the two classes. In view of the term 

 Sporozoa having become fixed in its extended usage, and the 

 phylogeny of the two groups being altogether hypothetical, 

 Reichenow (1929, 1935) divided the class Sporozoa into foxu" 

 distmct subclasses, viz., Telosporidia, Cnidosporidia, 

 Sarcosporidia, and Haplosporidia. Similarly Kudo (1931) 

 and Calkins (1933) divide the class Sporozoa into three 

 subclasses, Telosporidia, Cnidosporidia, and Acnido- 

 SPORIDIA, combining in the last the Sarcosporidia and Haplo- 

 sporidia. The balance of opinion at the moment does not 

 seem to favour the recognition of only two classes, but, if 

 this were done, they would be named Sporozoa {sensu stricto) 

 and Amcebosporidia. For practical convenience, and in 

 deference to general practice, I shaU follow Reichenow (1929, 

 1935) in dividing the class Sporozoa (sensu lato) into four 

 subclasses. 



The phylum PROTOZOA may thus be divided as follows :— 

 A. Subphylum Plasmodroma Doflein, 1901, emended. 



Movement effected by pseudopodia or fiagella, and syngamy 

 takes place, in all known cases, by the complete fusion of gametes. 



I. Class Mastigophoba Diesing, 1865. 



The predominating phase flagellate, locomotion being effected 

 by filamentous whip-like structures called flagella. The body 

 may be corticate or non-corticate. 



II. Class Rhizopoda von Siebold, 1845 ( = Sae,codina Hertwig & 

 Lesser, 1874). 

 The predominating phase amoeboid, locomotion being effected 

 by temporary extensions of the body called pseudopodia. 

 The body is non-corticate, i. e., has no tough limiting mem- 

 brane or cuticle. 



III. Class Sporozoa Leuckart, 1879. 



Exclusively parasitic forms which lack definite organs of loco- 

 motion. Reproduction takes place by spore-formation. 



(a) 1. Subclass Telosporidia Schaudinn, 1900 ( = Sporozoa 



sensu stricto). 



Trophozoite becomes full grown before reproduction 

 begins ; spore simple, with one to several sporozoites 

 or without resistant envelope ; the sporozoite a gre- 

 garinula ; asexual and sexual reproduction alternate 

 regularly. 



b2 



