STRUCTURAL DIFFERENTIA TIONS 



149 



transverse rows, making membranelles as broad as the peristome 

 (Fig. 174, p. 391). In the Vorticenida^ there are two rows of mem- 

 branelles the double adoral zone winding about the peristome 

 usually in a direction opposite to that of the Heterotrichida and 

 Hypotrichida (Fig. 78, p. 150). 



Undukitinc/ Memhranes. — Undulating membranes are found in all 

 orders of the ciliates and range in size from delicate aggregates no 

 broader from base to tip than ordinary cilia to relatively enormous 

 balloon-like structures ec{ual in width to more than half the diameter 



v^ 



r- 



^■^T* 



^ 



ti-' ,«•,*?''-"'"•«■.. 



?,-lK: 



Fig. 77. — Lemhadion conchoides F. F. (After Faure-Fremiet.) 



of the body, and in some cases as Lemhadion conchoides, almost equal 

 to length of the body (Fig. 77). In the simplest cases these mem- 

 branes are composed of a single row of longitudinally placed cilia, the 

 basal bodies of which form a single basal strand. Since cilia of the 

 longitudinal rows beat metachronously the result of their contraction 

 when fused in these undulating membranes is a series of waves 

 passing from the anterior to the posterior end. In more complex 

 forms undulating membranes may be composed of 3 to 10 rows of 

 cilia, fused in longitudinal rows, the length varying from a few 



