: ZOOLOGY sect. 



The form of the body is very varied : it may be ovoid (Fig. 

 L, 1), kidney-shaped Qi), trumpet-shaped {3), vase or cup-shaped 

 '., 9) ; produced into a long, flexible, neck-like process (5), or into 

 rge paired lappets (6') ; flattened from above downwards, or 

 ongated and divided into segments reminding us of those of 

 segmented worm {8). 



Most species are free-swimming, but some are attached to 

 eeds, stones, &c., by a stalk. This may be a purely cuticular 

 ructure {9), or may contain a prolongation of the cortex in the 

 rm of a delicate contractile axial fibre (Figs. 73 and 74, ax. /.), 

 hich serves to retract the Infusor, its contraction causing the 

 alk to coil up into a close spiral. 



The arrangement of the cilia is also subject to great varia- 

 on, and presents four chief types. In the holotrichous type, of 

 hich Paramoecium is an example, the cilia are all small, equal- 

 zed or nearly so, and arranged in longitudinal rows (Fig. 69, Fig. 

 1, 1). The second or heterotrichous type is seen in its simplest 

 irm in Nyctotherus (Fig. 71, 2), in which the left side of the 

 sristome is bordered by a row of specially large adoral cilia, the 

 ;st of the body being covered with small cilia. In Stentor (3) 

 le peristome is situated on the broad distal end of the trumpet- 

 laped body, and the adoral band of cilia takes a spiral course, 

 his leads us to the peritrichous type of ciliation : in Vorticella 

 ?'ig. 73) the vase-shaped body is, for the most part, quite bare of 

 lia, but around the thickened edge of the peristome passes one 

 mb of a spiral band of large cilia united at their bases, the other 

 mb being continued round a raised lid-like structure, or disc, into 

 hich the distal region is produced. This arrangement of cilia 

 caches its greatest complexity in Epistylis pKcatilis (Fig. 71, 9), 

 1 which the ciliary spiral makes no fewer than four turns. 



But it is in the hypotrichous type that the most extraordinary 

 lodifications are found. The flattened body bears on its dorsal 

 irface mere vestiges of cilia in the form of very minute processes 

 f the cuticle, while on the ventral surface the cilia take the form 

 f large hooks, fans, bristles, and plates with fringed ends (Fig. 71, 

 ). The hooks and plates do not vibrate rhythmically like 

 fdinary cilia, but are moved as a whole at the will of the animal, 

 lus acting as legs. The hypotrichous Ciliata, in fact, in addition 

 ) swimming freely in the water, creep over the surface of weeds, 

 c, very much after the manner of Woodlice. One of the most 

 itraordinary forms in this group is Diophrys (7), the size and 

 rrangement of its polymorphic cilia giving it a very grotesque 

 ppearance. In another genus {10) the distal end of the flask- 

 laped body bears a circlet of large fringed cilia, giving the animal 

 le appearance of a Rotifer {vide Section VII.). 



In addition to cilia, many genera possess delicate sheets of 

 rotoplasm or undulating membranes in connection with the 



