DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 151 



formations comparable with the rotation of protoplasm in Nitella 

 or circulation in Tradescantia. Axopodia of the motile Heliozoa, 

 axial filaments of the inactive species and stereoplasmic cor.s of 

 the rhizopodia may be regarded as successive phases in the modi- 

 fication of vibratile flagella. These types of pseudopodia have in 



Fig. 81. — Types of Ciliata. A, Uroleptus pisces (after Stein); B, Cyclotrichium 

 gigas (after Faure-Fremiet) ; C, Stentor polymorpha (after Biitschli) ; D, Nyctotherus 

 ovalis (original). 



common an enveloping layer of granular protoplasm, but filopodia 

 and lobopodia represent a different type, being made up in large 

 part, or entirely, of ectoplasm and without any evidence whatsoever 

 of kinetic elements. So-called "contractile elements" of this type 

 of pseudopodia are largely figments of the imagination. 



