1 8 THE PROTOZOA 



the forms which are now recognized as Heliozoa or Radiolaria, were 

 variously interpreted. Ehrenberg did great service in describing the 

 skeletons of many Radiolaria, especially of the fossil forms, but he 

 had no conception of their organization, and placed them with the 

 Bryozoa, Rotifera and Echinodermata as a special class (Tubulata). 

 Under the name, ActinopJiryens, Dujardin grouped the Heliozoa, 

 together with a modern subdivision of the Infusoria (Szictoria), as 

 " forms with slowly contractile appendages." The structure of the 

 Radiolaria was first made out by Huxley ('51), who recognized them 

 as Protozoa, and correctly compared TJialassicolla with the heliozoon 

 Actinosphcerium. The pseudopodia, however, were not recognized, 

 and he was inclined to regard these forms as higher in organization 

 than a single cell, and placed them between the Protozoa and the 

 Sponges. Johannes Muller('55 '58) first saw the resemblance between 

 the fine ray-like pseudopodia of the Radiolaria and of the Heliozoa, 

 and his pupils, Claparede and Lachmann ('58), discovered the same 

 granule-streaming in their pseudopodia that Schultze had observed in 

 some of the Rhizopoda. With these data, Miiller included the 

 Radiolaria and the Heliozoa in the class Rhizopoda of von Siebold, 

 under the name Rhizopoda radiaria, which was modified into its 

 modern form, Radiolaria, by another of his pupils, Ernst Haeckel 

 ('62). Four years later Haeckel ('66) separated the Radiolaria from 

 the similar fresh-water forms, to which he gave the name Heliozoa. 



The further subdivisions of the subclass Rhizopoda have been 

 made upon two bases having almost equal value. In one system 

 they are divided according to the nature of the pseudopodia into the 

 orders Lobosa (Amcebcza of Ehrenberg) and the Reticulariida (Reti- 

 ciilaria of Carpenter, '62). In the other they are subdivided accord- 

 ing to the absence or presence of a shell, into the orders Amcebida 

 (Ehbg.) and Testacea (M. Schultze, '54). 1 The former system is 

 adopted by Delage and Herouard, by Lankester and the English 

 zoologists generally ; the latter by Biitschli. A third order under the 

 name Mycetozoida, is usually included with the Amoebida and the 

 Reticulariida. Although generally recognized in part at least, by 

 zoologists as Protozoa, the taxonomic position of the organisms 

 included in this order is in dispute. Under the name Myxomycetes 

 they are included with the fungi by most botanists, while by the zool- 

 ogists they are usually placed as a class of the Rhizopoda under the 

 name Mycetozoa (de Bary, '59). The relation to the fungi is claimed 

 on account of their saprophytic mode of life (terrestrial forms), and 

 their mode of spore-formation in sporangia which are often compli- 

 cated by the presence of stalks, columellae, and other plant-like 



1 Thalamophora, R. Hertwig ('74) ; Foraminifera, d'Orbigny ('26). 



