208 The Sarcodina 



but contains no skeletal elements. In other genera, the capsule varies in 

 thickness and may be reduced to a thin membrane which binds the 

 skeletal structures together. With the apparent exception of Heterophrys, 

 the skeletal elements are siliceous. Aside from a few species such as 

 Lithocolla glohosa (108), in which foreign particles are cemented to a 

 thin capsule, the skeletal scales and spicules are products of the organism. 



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Fig. 5. 5. Acanthocystidina: A. Astrodisculus radians Greet, "gelatinous" 

 covering without scales; x575 approx. (after Penard). B. Pinaciophora fliivia- 

 tills Greef (diameter, 45-50fi), test composed of scales (after Penard). C. 

 AcantJiocystis rubella Penard (diameter, 23-27/i); portion of body showing 

 tangential scales; radially arranged spines are enclosed within the axopodia 

 (after P.). D. Cienkowskya mereschkowskyi (diameter about 60(a), a sessile 

 form; scales embedded in gelatinous mantle; distal portions of axopodia not 

 shown (after Villeneuve). E-G. Raphidocystis infestans Wetzel; cyst being 

 released from ruptured test (E) and freed cyst (F), x570; dividing form, 

 skeletal elements dissolved with HFl to show gelatinous envelope (G), x820 

 (after W.). H. Raphidiophrys pallida Schulze, x2.50 (after Penard). 



