PLEURONEMA. 149 



What I wish now to show in the Pleuronema is the triple, or 

 I might say even the quadruple, diversity of the vibrating cilia, 

 or in other words, a quadruple specialization 

 of one type of organs, by their manifold 

 offices ranking their possessors above those 

 of their class which attain to a less degree 

 of complicity in this respect. The most 

 prominent of these cilia are those which are *'* 91 - 



arranged in longitudinal rows (fig. 90, cl) over nearly the whole 

 extent of the body, and which most frequently are seen in a 

 quiet state, projecting far out from the surface like so many 

 fine, rigid bristles. In fact, the motions of this animal are so 

 lightning-like in rapidity that I have never seen this form of 

 cilia except when the body is in a quiet state, and therefore 

 I judge that, as they do not move then, they are the principal 

 organs of locomotion. There is on the right side a group of much 

 more heavily built cilia, (me,} which project from the oblique 

 furrow in which the mouth (m) is set. They are more particu- 

 larly devoted to producing currents in which the particles of 

 food may be brought to the mouth. We see, also, projecting 

 from the forward end of the oblique furrow, and near the ante- 

 rior edge of the mouth, (m,) one of those proboscis-like lashes (I) 

 which are so characteristic of the lower, ciliate Infusoria ; but yet 

 it would not seem to have the same office as in the latter, since 

 it is usually held in this position, apparently as rigid as if it 

 were a wire ; and only now and then does it move, by a sudden 



Fig. 89. Ceratimn cornutum. Clap. 300 diam. A marine infusorian, cov- 

 ered by a reticulated shell (testa). t, I 1 , the two halves of the testa ; h, the 

 horns of t ; I, the vibratory lashes ; U, base of I; w, w l , transverse rows of vibrat- 

 ing cilia ; c, the contractile [?]vesicle. From Claparede. 



Fig. 90. Pleuronema instabilis, n. sp. 1000 diam. From fresh water, m, 

 the mouth ; st, the food gathered in one mass , me, large cilia in the vestibule of 

 the mouth ; I, the single vibrating lash projecting from m; cl, vibratory cilia cov- 

 ering the body in rows ; si, the posterior, and sl l , the anterior saltatory cilium ; 

 cv, the contractile vesicle; n, the reproductive organ. Original. 



Fig. 91. Stentor pnlymorphus, Ehr. 300 diam. A very young individual, 

 turned upside down to compare with fig. 90. d, edge of the oblique furrow ; cv, 

 the contractile vesicle. From Claparede. 



