MORPHOLOGY 



51 



thocystis. The axial rod, which is composed of a number of fibrils 

 (Doeflein; Roskin, 1925; Rumjantzew and Wermel, 1925), arises 

 from the central body or the nucleus located in the approximate 

 center of the body, from each of the nuclei in multinucleate forms, 

 or from the zone between the ectoplasm and endoplasm (Fig. 6). 

 Although semipermanent in structure, the axial rod is easily ab- 

 sorbed and reformed. In the genera of Heliozoa not mentioned 

 above and in numerous radiolarians, the radiating filamentous 

 pseudopodia are so extremely delicate that it is difficult to determine 



en 



.-Ite 



c v 



kSX 



w 



7\A\. -| '"•-/ 



ec 



Fig. 6. Portion of Actinosphaerium eichhorni, X800 (Kiihn). ar, axial rod; 

 cv, contractile vacuole; ec, ectoplasm; en, endoplasm; n, nucleus. 



whether an axial rod exists in each or not, although they resemble 

 axopodia in general appearance. 



There is no sharp demarcation between the four types of pseudo- 

 podia, as there are transitional pseudopodia between any two of 

 them. For example, the pseudopodia formed by Arcella, Lesquer- 

 eusia, Hyalosphaenia, etc., resemble more lobopodia than filopodia, 

 though composed of the ectoplasm only. The pseudopodia of Actino- 

 monas, Elaeorhanis, Clathrulina, etc., may be looked upon as 

 transitional between rhizopodia and axopodia. 



While the pseudopodia formed by an individual are usually of 

 characteristic form and appearance, they may show an entirely 

 different appearance under different circumstances. According to 



