22 THE PROTOZOA 



ridia(F\g. f), and in the present classification form a fourth order of 

 the Sporozoa. A third order under the name H<zmosporidiida(\.2kfo& t 

 '94), includes the sporozoan parasites dwelling in blood-cells and 

 plasm of different vertebrates (Fig. 8). 



The Infusoria finally have been variously classified since von 

 Siebold restricted the term as given by Ledenmiiller (i76o-'63) to 

 its modern significance. Until their unicellular structure was defi- 

 nitely established, the various types were placed among the higher 

 animals, sometimes with the worms, sometimes with the Coelenterata. 

 Even Perty ('52), who was the first to bring the ciliated forms together 

 under their present name Ciliata, believed them to be combinations of 



Fig. 8. A blood parasite or Haemospore, Plasmodium malarice. Amoeboid, spore-forming and 

 sexual phases are shown. [WASIELEWSKY.] 



cells. He included the Suctoria and the Ciliata as subdivisions of 

 the Infusoria. Stein ('57), who put the classification of the Ciliata 

 upon its final modern basis, had previously confused the relations of 

 Suctoria and Ciliata in his Acineta-theory. Claparede and Lachmann 

 ('58-'6i), after showing that Stein's interpretation was incorrect, raised 

 those Infusoria which are provided with suctorial tentacles and are 

 ciliated only during the embryonic phases, to the grade of a separate 

 subclass to which they gave the modern name Suctoria (Fig. i, 



c, sy 



Since Stein's work there have been but few important changes in 

 the classification of the Infusoria. Butschli ('83~'88) divided the 

 Ciliata into two unequal groups distinguished by the nature of the 

 mouth parts, the Gymnostomata and the Trichostomata. Stein's sub- 

 divisions based upon the arrangement of the cilia are more simple, 

 however, and the advantage of Biitschli's division is somewhat ques- 

 tionable. 



C. ANIMALS AND PLANTS 



In determining the boundaries of the subkingdom Protozoa, two 

 very interesting controversies have arisen, one relating to the boun- 

 dary between animals and plants, the other to the relations of Protozoa 

 to Metazoa. The modern attitude toward the first of these problems 

 is well expressed by Delage ('96), who says : " The question is not so 

 important as it appears. From one point of view, and on purely 



!Cf. Stein, II ('67), p. 142. 



