IN TR OD UC TION 1 7 



as used by von Siebold, may be replaced by the more comprehensive 

 term Sarcodina, given by Biitschli ('83), while the term Rhizopoda 

 may be applied to one group (subclass), characterized by an amoeboid 

 or changeable adult condition, and with lobose or reticulate motile 

 processes or pseudopodia. 1 Two other subclasses are now universally 

 included in the Sarcodina, the Hcliozoa (Haeckel), or "sun animal- 



Fig. 3. A radiolarian, Actissa princeps Haeck. [HAECKEL.] 



The central capsule (c) separates the inner protoplasm (v) containing the nucleus (n) with its 

 cleolus (/), from the outer protoplasm which gives rise to the pseudopodia (_/). 



ila" (Fig. 2), characterized by fine ray-like pseudopodia, which often 

 mtain a central axial thread of stiffened protoplasm, and the 

 \adiolaria (Haeckel), characterized, in addition to the ray-like 

 pseudopodia, by the possession of a central portion of protoplasm, 

 which is surrounded by a perforated membrane, the " central capsule" 

 (Fig. 3). 



Before the modern system of classification was established, many of 



1 The term " pseudopodia" was given by von Siebold to replace Dujardin's more descriptive 

 phrase "changeable processes" {expansions variables}. 



