io6 



THE INVERTEBRATA 



layer may be absent. In Paramecium the cortex is covered by a thick 

 pellicle which possibly contains a minute alveolar layer. 



rid. tri. fl! 



B 



Fig. 85. Details ofthe ectoplasm of ciliates. After Wetzel. A, Frontonia leucas 

 (Vestibulata). B, Paramecium. C, The same, surface view. alv. alveolar layer; 

 ba.gr. basal granules; cor. cortex; enp. endoplasm ; yZ. flagellum;^.' insertion 

 of flagellum ; pel. pellicle ; rid. ridges of pellicle ; tri. trichocyst. 



Order HOLOTRICHA (ASPIRIGERA) 



Ciliata which do not possess an adoral wreath ; and which nearly all 

 have uniform ciliation of the whole surface of the body. 



This order is a collection of relatively simply organized ciliates, 

 some of which are primitive while others are degenerate through 

 parasitism. 



Suborder PROCILIATA 



Holotricha without mouth ; and without differentiation of meganuclei 

 from micronuclei. 



Opalina (Figs. 5, 21 C, 86). With several, usually many, nuclei, 

 which are all alike. In each nucleus, however, there can be dis- 



Fig. 86. Opalina ranarum. From Borradaile. A, Ordinary individual in 

 longitudinal fission. B, The same in transverse fission. C, Small encysted 

 individual (distributive phase). D, Gamete. E, Encysted zygote. 



