DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 145 



ture, or a form-rectifying organ, in these parasitic types is difficult 

 to conceive. On the other hand, their intimate relation to the 

 blepharoplasts and their activity in reproduction indicate a common 

 function with the kinetic elements. The observations of Kofoid 

 and Swezy on the energetic movements of the axostyle while the 

 organism works its way through the mucus afford a more plausible 

 interpretation of the function of this organoid than the a priori 

 view of those who see in such movements only the efforts of an 

 elastic supporting structure to restore the form of a plastic cell. 



Fig. 



■Trichomonas augusta Alex. Two successive stages in division of the axo- 

 style. (After Kofoid and Swezy.) 



2. Pseudopodia. — Pseudopodia are more or less temporary' pro- 

 jections of the cortex which may serve for purposes of locomotion 

 or, more often, as food-trapping or food-catching organoids. Four 

 types are recognized, axopodia, rhizopodia (myxopodia), filopodia 

 and lobopodia, which differ widely in their structural make up. 

 Of these only the first type can be regarded in a strict sense as 

 motile organs (see p. 140), the others functioning as food-catching 

 organoids, or mere protrusions of the semifluid body. 



Axopodia.— Axopodia are different from other types of pseudo- 

 podia in possessing, like flagella, central axial fibers of specialized 

 protoplasm derived from endoplasmic kinetic elements. They are 

 found only in organisms belonging to the groups Heliozoa and 

 10 



