^ IIBITISH FEESHWATER HELIOZOA. 



principally among the various French and German 

 scientific publications. 



Leidy's systematic work on the Rhizopoda of the 

 United States (1879) includes numerous records and 

 figures of Heliozoa, but many of them cannot be 

 absolutely identified owing to the absence of any 

 indication of the necegsary specific characteristics. 



During the last decade of the nineteenth century 

 interest in this group much revived when Brauer, 

 Hertwig and Schaudinn amongst others devoted their 

 attention to their life-histories. In 1904 Penard pub- 

 lished his systematic monograph of the freshwater 



~-> 



Pig. 177.— Copy of a figure in Briglitwell's ' Infusoria of E. Norfolk,' 

 representing Actinosphierium eichhornii. 



forms ('Les Heliozoaires d'eau douce,' Geneve), add- 

 ing much to our biological knowledge of them and 

 describing many new species. 



STltUCTUKE. 



The stiff axes usually present in the radiatino- 

 pseudopodia distinguish the Heliozoa from the Rhizo""- 

 poda and the Foraminifera, and the absence of a 

 central capsule from the Radiolaria. 



Nearly all the Heliozoa possess some kind of silicious 

 or chitinous spherical investment, and their classifica- 

 tion is based on its nature. 



The Chalarothoraca, or typical Heliozoa, are charac- 

 terised by possessing skeletons which can usually be 

 identified more or less readily by the forms of the 



