Cilia

“ The cilia themselves have a stiffer basal part, probably strengthened by an axial rod, and a distal flexible lash; when cilia are united by the outer plasmatic layer, they form (1) “Cirrhi,” stiff and either hook-like and pointed at the end, or brush-like, with a frayed apex; (2) membranelles, flattened organs composed of a number of cilia fused side by side, sometimes on a single row, sometimes on two rows approximated at either end so as to form a narrow oval, the membranelle thus being hollow ”

“ Turning his microscope in all directions, he examined water and found it peopled with minute animalcules, those simple forms of animal life propelled through the water by innumerable hair-like cilia extending from the body like banks of oars from a galley, except that in many cases they extend from all surfaces. He saw not only the animalcules, but also the cilia that move their bodies. ”

“ There seems to be no choice in the matter; contact with any substance gives rise, as an organic response, to the lessening or cessation of the regular movements in all the cilia except those of the mouth-groove and funnel. As the Paramecia swim hither and thither, first one, then another, then more, chance to come in contact with the bacterial clot, the blotting-paper, or other substance, and since the lashing of the cilia is then automatically lessened, there they stay; others find their way to the same spot in the course of their random movements, and they, too, stay ”

“ The free-swimming larvae escape by the osculum; they are minute oval bodies moving rapidly by means of a covering of cilia. The greater part of the body is a dazzling white, while the hinder pole is of a brown violet colour. This coloured patch is non-ciliate, the general covering of cilia ending at its edge in a ring of cilia twice the length of the others. Forward {173}movement takes place in a screw line; when this ceases the larva rests on its hinder pole, and the cilia cause it to turn round on its axis. ”

“ The body of the Ciliata usually is bilaterally symmetrical and is enveloped in a cuticle which has numerous openings for the protrusion of the cilia. Most kinds have a fixed shape, whilst changes in the form of others are brought about by the contractions of the body substance. The latter exhibits hyaline ectoplasm, in which myonemes, and occasionally also trichocysts (minute spindle-shaped bodies) appear, and granular endoplasm which may contain numerous vacuoles. The cilia, on whose various arrangements the classification is based, are always processes of the ectoplasm. ”

“ The cilia are under the control of the animal in the same way as the legs and arms of a man are under his control. Now supposing that the bodies of these organisms became unsymmetrical{132} during the phylogenetic history and as a result became unable to continue to swim in a straight path, the pertinent question to ask is: Was it easier for these organisms to learn to revolve on their long axis than to learn to beat their cilia a little harder on the side toward which they swerved? Observation of the forms before us does not afford any evidence that rotation was the easiest solution. ”

“ The edge of the opening of the shoe is bordered by a fringe of cilia, the ciliary movements of 389 which keep the microscopically small and transparent nurse swimming about freely in the sea. This fringe of cilia is marked in Fig. A 2-A 4, on Plate VII., by the narrow alternately light and dark seam. The nurse then, in the first place, forms a perfectly simple intestinal canal for nutrition, mouth (o) , stomach (m) and anus (a) . Later, the windings of the fringe of cilia become more complicated, and there arise arm-like processes (Fig. A 3-D 3) . ”

“ They have cilia externally, and a cutis which secretes similar hyaline tubes to those of many Annelida. The muscular system ia greatly developed, and iu definite layers, and many swini as freely as the most active leeches. The digestive system intimately agrees, having cilia on the inner surface of the canal, a muscular cesophageal region, and a sacculated intestine, while the glandular and other elements in the wall are very similar; it differs in not passing through a buccal nervous collar, although it lies beneath the nervous system in this region. ”

“ It consists of a compact gland-like organ, containing a much coiled tube, ciliated for the greater part of its length, but deprived of cilia in its last coils; this latter part—or duct—leaves the "gland" and pierces the body-wall, opening to the exterior at the base of the parapodium. The ciliated canal passes forwards into the next segment, where it opens by a funnel into the coelom. The lip of the funnel is extremely curious, for the cells constituting it are drawn out into very long, delicate processes covered with cilia. [307]
Fig. ”

“ These cilia all lash the water in one direction, and so drive the little body along as if it were propelled by thousands of extremely minute paddles. After enjoying its freedom for a longer or shorter time, and being carried either by the force of its own cilia, or by currents which bear it along, the embryo coral settles down to the bottom, loses its cilia, and becomes fixed to the rock, gradually assuming the polype form and growing up to the size of its parent. ”

“ If we examine a single specimen under a high power of the microscope we shall see its shape, which, when fully extended, is long and cylindrical, having at one end a mouth surrounded, as is usually the case in the infusoria, by a circle of very fine hairs, or cilia, as they are called, from the Latin word cilium an eyelash; the mouth opens into a long narrow channel; the creature's throat, which leads to its stomach; towards the opposite extremity the animal [Pg 18] tapers, till it ends in an extremely long fine hair-like tail which is fixed in the jelly-like ball ”

“ The movements of the cilia are co-ordinated and they act in concert, though not absolutely in unison, each one contracting just before or after its neighbour, so that waves of movement pass over a ciliated surface in a given direction, similar to what may be seen in a cornfield when the wind is blowing over it. ”

“ Order I.—Section A.—Gymnostomaceae. Mouth habitually closed; swallowing an active process; cilia (or membranelles) uniform, usually distributed evenly over the body; form variable, sometimes of circular transverse section.
Section B.—Trichostomata. Mouth permanently open against the endosarc, provided with 1 or 2 undulating membranes often prolonged into an inturned pharynx; ingestion by action of oral ciliary apparatus.
Order 2.—Subsection (a) .—Aspirotrichaceae. Cilia nearly uniform, not associated with cirrhi or membranelles, nor forming a peristomial wreath. ”

“ Mouth in the anterior third of the body. The left edge of the mouth carries a distinct undulating membrane; the right edge is plain, longitudinally striated and bears cilia. It is slightly depressed and the depression is carried posteriorly in the form of a shallow furrow which reaches to the posterior end. The contractile vacuole is on the left side, the spheroidal nucleus on the right side of the furrow. The body is uniformly covered with fine cilia, and the periphery is uniformly studded with large trichocysts, except along the furrow. Food consists of dinoflagellates and other small forms. ”

“ These coloured particles can readily be traced in their movements, and accordingly we see them tossed about and whirled about by the ciliary currents, and finally swept into the mouths of the animalcules, which appear always to be on the outlook, if one may so term it, for nutritive matter. Sometimes when we may be unable to see the cilia themselves, on account of the delicate structure, we may assure ourselves of their presence by noting the currents they create. ”

“ The rotating organs from which these fascinating animalcula derive their name consist of two disc-like bodies whose margins are fringed with rows of cilia, which create currents toward the oral aperture, and which have given rise to the optical delusion of rotating wheels. The disposition of the cilia is so arranged as to bring food to the rotifer and conduct it to the mastax or digesting apparatus—a muscular bulb moved by a series of muscles—the gastric glands and stomach. The great transparency of the whole structure permits of the animal economy being easily studied. ”

“ The little animals are provided with exceedingly fine cilia that they keep in almost constant motion; no one knows how, or for what, but it is supposed they thus sweep in the water that circulates through all the channels and chambers formed for it. After death, the soft matter, like all animal tissues, decays, or is dried up ”

“ Some possess shells (fig. iii. 3, 5, 21, 22, 25, 26) , most have a distinct swallowing apparatus, and in Dysteria there is a complex jaw—or tooth-apparatus, which needs new investigation. In the active Ciliata we find locomotive organs of most varied kinds: tail-springs, cirrhi for crawling and darting, cilia and membranellae for continuous swimming in the open or gliding over surfaces or waltzing on the substratum (Trichodina, fig. iii. 8) or for eddying in wild turns through the water (Strombidium, Tintinnus, Halteria) . ”

“ These currents are rendered evident by floating particles in the water. The possession of these vibratile cilia is not peculiar to this class of animals; indeed, there is good reason to believe that there is scarcely a living creature, from the lowest animalcule, or plant germ, up to man himself, that is not provided with them in some part or other. In many of these Infusoria the cilia constitute the organs of locomotion ”

“ In one group of infusoria (Hypotricha) , the cilia, “cirri,” have attained a high degree of differentiation, and reach a considerable size. Both cilia and flagella spring directly from the cell-protoplasm, piercing the cell-membrane, when this is present. At the point where they become continuous with the cell-body there is usually a deeply staining “basal granule.” In some cases the flagella are in direct connexion with the centrosome (see below, Cell-division) , e.g. ”

“ This wandering half or head is now seen to be provided at each end with cilia, and by means of these filaments swims freely throughout the surrounding water. After a time, however, it settles down, develops a stalk from what was originally its mouth extremity; whilst the opposite or lower extremity with its fringe of cilia comes to represent the mouth of the new animalcule. We thus note that new bell-animalcules may be produced by the division of the original body into two halves. They also increase by a process of budding. New buds grow out from the body near the attachment of the stalk ”

“ The first is, in its most primitive form, a small transparent creature, with a mouth and anus and a postoral longitudinal ciliated band (fig. 5, A) . In Asteroids the band of cilia becomes divided in such a way as to give rise to two bands, the one preoral, encircling the preoral lobe, and the other remaining postoral (fig. 5, B) . In the other groups the band remains single and longitudinal. In all cases the edges of the body carrying the ciliary bands become sinuous (fig. 6) and sometimes prolonged into arms (figs. 7-9) , and each of the four groups has its own type of larva. ”

“ On this level, too, lie the dot-like granules at the bases of the cilia, which form definite groups in the case of such organs as are composed of fused cilia; in the deeper part of the ectoplasm the vacuoles or alveoli are more numerous, and reserve granules are also found; here too exist the canals, sometimes developed into a complex network, which open into the contractile vacuole. ”

“ In some cases an external layer is formed of agglutinated sand-particles; in others of imbricated plates, as in Coccospheres; and in many others radiating spicules stand out on all sides. Throughout sundry classes the exoplasm develops cilia, by the wavings of which the creatures are propelled through the water—cilia which may be either general or local. And then this cortical layer, instead of being spherical or spheroidal, may become plano-spiral, cyclical, crosier-shaped, and often many-chambered; whence there is a transition to colonies. ”

“ You will find plenty of infusoria in any stagnant water, and when placed under the microscope a mouth may be perceived, but no stomach, nor any apparent receptacle for food, which appears to enter at once into the body substance. The other kinds capture their food by seizure by the tentacles, or by agitating the cilia, like the flagellata, and thus whipping the nourishment towards the mouth, as children will draw in a toy boat to land by agitating the water in the given direction. These cilia, or hairs, serve for organs of locomotion as well as of capture. ”

“ Those most frequently met with, and which attract the most attention from observers, are furnished with vibratile cilia, which cover the whole body, acting as paddles. These organs are evidently intended to propel the animal from one place to another. At other times they appear to be employed in conveying food to the mouth, if we may use the expression. Some Infusoria are without these cilia, having only one or many very slender filaments, the undulating movement of which suffices to determine their progression through the liquid which surrounds them. ”

“ Then it thrusts out its tail-foot, swells its body to an oval globe, protrudes its feeler, and slightly [80] exposes a row of cilia. After this two distinct wheels are everted, and as their cilia whirl and spin, the animal is swiftly rowed along, until it thinks proper to moor itself fast by the tail-foot, and employ all its ciliary power in causing currents to converge towards its throat. When it pleases it can elongate the body, till it becomes vermiform, and it walks like the common rotifer, by curving its back, and bringing its nose and its tail in contact with the ground. ”