INFUSORIA. 



[ 416 ] 



TNFUSOEIA. 



structure can be detected in the Infusoria, 

 but a contractile power is possessed by the 

 general substance of the body. In Vorticella 

 (PI. 32. figs. 21 a & 20) and some others, the 

 contractile substance is prolonged through 

 the hoUow pedicle, thus forming a spurious 

 muscular baud. 



The other directly or indirectly locomo- 

 tive organs are thus distinguished. 1, cilia: 

 these are the most common, and form the 

 fine, short, very transparent, hair-like fila- 

 ments projecting from the surface. In 

 some they entirely cover the surface, whilst 

 in others they are arranged in one or more 

 rows round the mouth or upon the ventral 

 sm-face, &c., as described under the genera. 

 During life they are seen actively vibrating ; 

 and in some their motion appears constant ; 

 whilst in others it is interrupted at inter- 

 vals, apparently under the influence of a 

 will. They are most distinctly seen when 

 the Infusoria are dried (see Cilia). 2, fla- 

 gelliform filaments (PI. 31. fig. 59), which 

 are long anterior cilia, the ends alone being 

 vibratory and movable in all directions ; 

 there are usually one or two only. 3, re- 

 tracting ciha or filaments (PI. 30. fig. 12, 

 18 a ; PI. 31. fig. 17) : these are single, long, 

 flexuous, and directed backwards ; they fre- 

 quently become adherent to the slide, and 

 produce a sudden, backward motion of the 

 animal. 4, setge or bristles (PI. 31. fig. 53) : 

 these are rigid, filiform, straight, and mo- 

 vable, but not vibratile, and are sometimes 

 provided with a bulb at the base ; they can 

 be slowly raised or depressed, and serve for 

 support, walking, or climbing. 5, styles 

 (PI. 32. fig. 17) are thick, straight, very 

 movable setaj, without bulbs, sometimes 

 having setiform branches ; they neither ro- 

 tate nor vibrate. 6, uncini or hooks (PI. 50. 

 fig. 13) are short, thick, curved, sometimes 

 cleft setfe, serving for prehension, climbing, 

 or creeping, and are bidbous and usually 

 very thick at the base. 



The long straight cirri of Halteria (PI. 50. 

 fix. 12), by which the saltation of these 

 Infusoria is produced, probably come under 

 the fifth series ; but the foot of such genera 

 as Dysteria (ErviUa, Duj.) (PI. 30. fig. 52), 

 which is used for locomotion, and also as a 

 peduncle, is the homologue of the contractile 

 sai'code in the hollow peduncle of VorticeUa. 



The flageUum of a marine Ceratium which 

 was observed by Claparede, suddenly disap- 

 peared during a rapid contraction. _ It re- 

 tracted into a spherical cavity, which was 

 placed close to its point of insertion. 



Nervous system. — Xone has been disco- 

 vered. In the naked Infusoria, the sense of 

 touch is difiUsed throughout the substance 

 of the body. In others, it is particularly 

 developed in the snout-like appendages of 

 the body, and in the longer cilia, sette, &c. 

 The Infusoria are probably all sensible to 

 light ; and many of them exhibit, near the 

 anterior part of the body, one or more 

 coloured (mostly red) specks, which have 

 been regarded as eyes; but they contain 

 no distinguishable cornea, nor lens, nor are 

 they connected with any appreciable sub- 

 stance comparable to nervous matter. 



The pigment-spot is composed of a col- 

 lection of minute and highly refracting 

 granules, and in some species it is associ- 

 ated with Lieberkiihn's " watchglass-like 

 organ." This is a very minute, transparent, 

 colourless and hard part of the cortical 

 layer, which has its convex side towards the 

 pigment-spot and the concave towards the 

 head ; but it is not dependent on the pre- 

 sence of the pigment, for some species 

 possess it which have no pigment-spot, and 

 vice versa. Similar specks occur in the same 

 situation in the spores of many Algfe ; more- 

 over the eye-specks are most distinct in those 

 genera which are doubtful Infusoria. Hence 

 it may be denied that they represent eyes ; 

 yet they bear considerable resemblance to 

 the eyes of the Rotatoria and some Anne- 

 lida ; so that their true nature must be con- 

 sidered doubtful. 



Digestive system. — On attentively exami- 

 ning Infusoria under a high power (1-4 to 

 1-8), a number of rounded spots are gene- 

 rally visible in the substance of the body ; 

 they are sometimes filled with a whitish 

 granular matter ; at others they contain 

 Desmidiacese, Diatomacepe, or other AlgiB 

 or bodies existing in the surrounding water. 

 These have been called gastric vesicles, cells, 

 spaces, vacuoles, or sacculi. They are only 

 visible from their contents, and no mem- 

 brane can be distinguished in them. If a 

 little indigo or carmine be added to the 

 water containing the Infusoria, these cavi- 

 ties will soon become filled and will be 

 rendered very distinct ; in the Plates they 

 are represented as fiUed with these pig- 

 ments. 



On attentively watching them, they wiU 

 appear to move around the body of the ani- 

 malcule, sometimes two of them appearing 

 to become fused into each other, or the con- 

 tents of one to pass into another. Finally, 

 the pigment will be seen to escape at some 



