Lectures on the comparative anatomy and physiology of the vertebrate animals : delivered at the Royal College of Surgeons of England, in 1844 and 1846 ... Part 1. Fishes / by Richard Owen.

Date:
1846
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on the comparative anatomy and physiology of the vertebrate animals : delivered at the Royal College of Surgeons of England, in 1844 and 1846 ... Part 1. Fishes / by Richard Owen. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    The locomotive Polygastria propel themselves through the water by the action of their vibratile cilia, which are sometimes generally dif- fused, as in Bursaria and Nassula ; sometimes aggregated, in longi- tudinal rows, as in Amj)hileptus; often limited to the region of the mouth, as in the Vorticella, indicating the passage to the higher or Rotiferous group. These cilia in some species, as in Stylonychia and Eiiplotes, are of such relative size as to give the species a myriapodous character, and are used, like little feet, to creep along the stems of the Chara, and other minute vegetable plants. True jointed locomotive members are never developed in any of this minute and primitive race of animated beings; but they retain, throughout life, those simple vibratile cilia which produce the rotatory movements in the ova of Mollusca Avhilst imprisoned in their nidus, which are probably the agents of analogous movements of the ovum of the Mammalia in the Fallopian tube, and which are doubtless common to the ova of all classes of animals at that early period which the Polygastric Infusoria seem permanently to represent. These cilia, the outward instruments of locomotion in Infusoria, and which are retained in greater or less proportion on the epithelium- clad mucous surfaces of all animals, appeal', notwithstanding their minute size and incalculable numbers, to owe their motions to the actions of definitely arranged muscles : Ehrenberg has seen the ex- panded base of the locomotive cilium in the Polygastria, and describes the radiated structure which he conceives to indicate the disposition of the muscular fibres moving such cilium. If you watch the motions of the Polygastric Infusoria, you will perceive that they avoid obstacles to their progress ; rarely jostle one another; yet it is difficult to detect any definite cause or object of their movements. Some species, it is true, prey upon animalcules of their own class, and will gorge an individual of nearly their own size, which they attract by the currents in the water caused by the oral vibratile cilia. But the greater number of the class subsist on the minute atoms of the decomposing animal and vegetable substances of the fluids or infusions in which they exist,—particles which do not require a definite pursuit, since they are inert and generally diffused throughout the infusion. The motions of the Polygastria have appeared to me, long watching them for indications of volition, to be in genei'al of the nature of respiratory acts rather than attempts to obtain food or avoid danger. Very seldom can they be construed as voluntary, but seem rather to be automatic ; governed by the influence of stimuli, within or without tlie body, not felt, but reflected upon the contractile fibre; and therefore are motions which never tire. We may thus explain the c 2