204 The Sarcodina 



podia has been discussed by Roskin (126). The inner and peripheral zones 

 of cytoplasm are not separated by a central capsule. Most Heliozoida are 

 approximately spherical floating types, and except for a few species of 

 Acanthocystis, Camptonema, and certain other genera, occur in fresh 

 water. The recognition of typical Heliozoida is easy enough. However, 

 it is difficult to detect axonemes in the delicate pseudopodia of certain 



/ 7/ / I \ \ '• 



B 



Fig. 5. 2. Basic morphological types in Heliozoida; diagrammatic. A. Acan 

 thocystis-type: test composed of separate plates, spines sometimes present 

 nucleus not central; axopodia radiate from a central granule. B. Clathrulina 

 type, as in Desmothoracina: perforated test not composed of separate scales; 

 stalk often present. C. Acti7iophrys-type: no test; nucleus approximately cen 

 tral in uninucleate forms. D. Nuclear division in Acanthocystis aculeata, show 

 ing supposed central granules at the poles of the spindle; xlOlO (after Belar) 



forms and there are some species in which axonemes have not yet been 

 reported. 



With respect to the peripheral cytoplasm and its derivatives, Heliozoida 

 may be divided into naked types and those which secrete some sort of a 

 test. The test may contain discrete scales or spines (Fig. 5. 2, A), or it 

 may be a continuous capsule containing many pores (Fig. 5. 2, B). In 

 such naked types as Actinophrys (Fig. 5. 2, C), the outer cytoplasm con- 

 tains many vacuoles, one or more of which may be contractile. The vac- 

 uolated layer encloses a thick granular zone of cytoplasm within which, 

 in uninucleate species, a large nucleus is more or less centrally located. 



