478 



BIOLOOY OF THE PROTOZOA 



degrees of specialization and that some forms may carry on all 

 processes of asexual activity without a micronucleus and these may 

 represent transition stages to the condition in opalinids in which 

 there is no nuclear dimorphism at all and both sexual and asexual 

 processes are possible with only one type of nucleus. According to 

 McNally this is the condition in Nassula ornata or N. elegans. 



The kinetic elements, including cilia and their derivatives and 

 coordinated systems of intracellular fibrils, represent a neuromotor 

 apparatus even more complex than that of the higher flagel- 

 lates. In but few cases are there combinations of other types of 

 motile organs with cilia. One such case is described by Penard 

 under the name Myriaphrys paradoxa, a form with axopodia and 

 cilia (Fig. 197); another is a combination of cilia with a flagellum, 



Fig. 197. — Myriaphrys paradoxa (?), with cilia arid axopodia. (After Penard. 



Monomastix (-Hiatus described by Schewiakoff. The possibility of 

 the derivation of ciliates from flagellates, in some cases through 

 Heliozoa-like forms, is suggested by such types, but origin of this 

 group involves far too much speculation for serious consideration. 



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

 Chapter IV). Undulating membranes, meinbranelles and cirri are 

 present in the majority of ciliates. A fourth type of combination, 

 membranulae or pectinelles, combines several of the features of 

 flagella. Thus the powerful motile organs of Didinium are composed 

 of a few flagella-like, long cilia, while rhizoplasts run from their 

 basal bodies to the vicinity of the nucleus (Fig. 98, p. 187). 



Undulating membranes are limited regionally, to the gullet, 

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

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



