A handbook to the cases illustrating animal locomotion / Horniman Museum and Library.
- Horniman Museum
- Date:
- 1912
Licence: In copyright
Credit: A handbook to the cases illustrating animal locomotion / Horniman Museum and Library. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![HANDBOOK TO THE CASES ILLUSTRATING ANIMAL LOCOMOTION. SWIMMING. [Cases 10 to 20 and table-case.] The sea may be regarded as the probable place of origin of animal life in the past, but whilst many kinds of animals are of purely aquatic descent, others have become re-adapted to life in water after an interval of modification for a terres- trial existence. It is not surprising, therefore, that there should be great variety in the adaptations for swimming found amongst aquatic animals. PROTOZOA.—Many Protozoa swim by means of cilia. The slipper animalcule (Paramecium caudatum), a protozoon just visible to the naked eye as a whitish speck and commonly found in large numbers in water containing decaying vegetable matter, is an example. Each cilium is a delicate thread-like process of the animal, and by alternate bendings and straight- enings of the whole of the cilia the Paramecium swims through the water. Other kinds of protozoa swim by means of flagella. A flagellum, like a cilium, is merely a slender process of the body, but the flagellum differs from the cilium in being longer and projecting from the front end of the body; by means of lashing movements it drags the protozoon after it, instead of driving it forward. Euglena viridis is an example of a protozoon with one flagellum, Polytoma uvella of a protozoon with two flagella. CCELENTERATA.—The jelly-fishes, of which Rhizostoma pulmo is shown as an example, have usually broad, umbrella- shaped bodies. By rhythmical contractions of the umbrella, water is forced out of the concavity of the umbrella, and by this means the animal is driven along. Jelly-fishes are, however, poor swimmers, and are quite unfitted for making headway against currents or tides. The pulsations of the umbrella’may be occasionally observed in specimens of the common jelly-fish (Aurelia aurita) which have been left in rock pools by the tide.](https://iiif.wellcomecollection.org/image/b22486185_0013.jp2/full/800%2C/0/default.jpg)
