166 



CLASS: RHIZOPODA 



Heliozoa are popularly known as sun animalcules, and are mostly found 

 in fresh water. Two common forms are Actinosphcerhwi eichhorni (Fig. 71), 

 which is multinucleated, and Actinophrys sol (Fig. 75), which has a single 

 nucleus. Both have been much studied from the point of their nuclear 

 divisions and pedogamy, as described above (p. 86). Members of the genus 



Fig. 76. — Vampyrella later itia : A Single Individual at Different Stages of its 

 Attack on an Alga ( x 300). (After Cash, 1905.) 



1. The free individual. 2. The same applied to the surface of the filament. 



3. The filament has been broken, and one segment evacuated. 



4. Later stage with four segments detached, two of which are evacuated. 



VampyreUa are parasitic forms which bore their way into the cells of alga), 

 in which they live and multiply (Fig. 76). Another genus, Nuclearia, 

 parasitizes not only algse, but also other Protozoa. 



3. Order: RADIOLARIA Haeckel, 1861. 



The members of this order, like those of the preceding one, show 

 a tendency towards a radial arrangement of the pseudopodia, but 

 morphologically they are more complicated than the Heliozoa. Various 

 skeletal structures are commonly produced, while a perforated mem- 

 branous structure, the capsule, divides the cytoplasm into a central 

 intracapsular portion, which contains the nucleus, and an extra- 



