Zoology : a description of types of animal structure / by Andrew Wilson.

  • Andrew Wilson
Date:
1877
Catalogue details

Licence: Public Domain Mark

Credit: Zoology : a description of types of animal structure / by Andrew Wilson. Source: Wellcome Collection.

    16/160 (page 12)
    remains apparent for a time as a ‘food-vacuole/ which, however, soon closes up and disappears. The food- vacuoles are in all probability caused by the presence of water or of some other fluid. If any part of the food is found to be indigestible, it is simply cast out of the body through a temporary opening formed in the ectosarc, just as when the food was received or ingested ; whilst in som£ amoebae a special portion of the body, named the villous region (fig. 2, B, v), has been alleged by some observers to be that by or at which indigestible portions of food are rejected. 7. Circulation in Amosba.—The result of the digestion of food in all living beings is to produce a fluid—named blood in animals, and sap in plants—from which the body can gain a supply of fresh nutrient matter, and thus repair the wear and tear which is inevitably associated with the act of living and being. This fluid is usually circulated through- out the body so as to bring it in contact with each tissue or part of the body; and in higher animals, the heart and blood-vessels or analogous organs perform this duty. Although the simplicity of the amoeba’s body forbids us to expect to find therein the perfection of detail exhibited by higher beings, it nevertheless appears probable that the contractile vesicles represent a circulatory apparatus in its most primitive state. At the moment of contraction or systole of these vesicles, tubes or canals are described by some authorities as having been observed to pass from the vesicles to the surrounding protoplasm ; and we know that in certain near neighbours of the amoeba—the Infusorian animalcules—these radiating spaces or canals actually occur. But apart from these observations, the mere fact of these vesicles contracting so regularly would strongly suggest the probability and correctness of the idea that their function is that of circulating some fluid or other throughout the organism. Innervation of Amoeba.—No traces whatever of a nervous system or organs of sense, whereby the amoeba might be brought into relation with the outer world and thus gain a knowledge of its surroundings, can be discerned. That the organism can and does exercise some means of gaining