II] 



HEL1OZOA 



31 



spore divides twice, but one daughter of each division is absorbed 

 so that one residual nucleus remains after both divisions. Then 

 the secondary cyst walls break down and the residual nucleus 

 in each spore unites with its fellow forming a zygote which after a 

 time germinates and grows into a new Actinosphaerium. Amoebidea, 

 Thalamophora, Radiolaria and Heliozoa on account of their power 

 of emitting pseudopodia are sometimes united in one large division 

 called Rhizopoda. 



FIG 9 Actwosphaerium eicMiornii x 200. From Leidy. The endoplasm is 

 ' crowded with food vacuoles containing Diatoms, and nuclei are represented 



in the figure by the dark areas. 



1. Contractile vacuole. 2. Food vacuole which has just swallowed a Kotifer. 

 3. Pseudopodia. 



The next group of the Protozoa we shall consider is a very large 



and important one. It is called the Flagellata. 



Fiageiiata. ^ mem ^ ers O f ft a re characterised by having one or 



more flagella, that is whip-like threads, which lash about in the 



