SPECIAL MORPHOLOGY AND TAXONOMY OF INFUSORIA 369 



dimorphism at all and both sexual and asexual processes are possible 

 with only one type of nucleus. 



The kinetic elements, including cilia and their derivatives and 

 coordinated systems of intracellular fibrils, represent a neuro- 

 motor apparatus quite as complex as that of the higher flagellates. 

 In but few cases are there combinations of other motile organs with 

 cilia. One such case is described by Penard inider the name 

 Mi/riaphrys paradoxa, a form with axopodia and cilia (Fig. 160) ; 

 another is a combination of cilia with a flagellum Monomasiix 

 ciliatus described by Schewiakoft'. The possibility of the derivation 

 of ciliates from flagellates, in some cases through Heliozoa-like 

 forms, is suggested by such t\pes, but origin of this group involves 

 far too much speculation for serious consideration. 



Fig. 160.— Mijriaphrijs paradoxa (?), with cilia and axopodia. (After Penard.) 



Cilia, by fusion, form locomotor organs of complex nature (see 

 Chapter III). Undulating membranes, membranelles and cirri, 

 are present in three of the four Orders of ciliates, while undulating 

 membranes are represented in all. A fourth type of combination, 

 membranula?, combines several of the features of flagella. Thus 

 the powerful motile organs of Didiniviii are composed of a few 

 flagella-like, long cilia, while rhizoplasts run from their basal bodies 

 to the vicinity of the nucleus (Fig. 161, 8). 



Undulating membranes are limited regionally, to the gullet, 

 margin of the mouth or to a circumscribed area called the peristome. 

 Membranelles are grouped usually, in a curved row the "adoral 

 zone" around the margin of the peristome, but a dorsal ring of 

 membranelles is present in some parasitic forms {c. g., Diplodiniun/, 

 P'ig. 2, p. 20). Cirri are combinations of cilia of usually, the ventral 

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