A junior course of practical zoology / by A. Milnes Marshall and C. Herbert Hurst.

  • Marshall, A. Milnes (Arthur Milnes), 1852-1893.
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: A junior course of practical zoology / by A. Milnes Marshall and C. Herbert Hurst. Source: Wellcome Collection.

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    e. The oral groove runs obliquely backwards along the ventral surface from near the anterior end to the mouth, which is placed a little behind the middle of the length of the animal. Its cilia are directed towards the mouth, and drive water and food- particles into it. f. The mouth is an oval aperture in the ectosarc at the hinder end of the oral groove, through which the food passes into the endosarc. g. The anus is an aperture between the mouth and the hinder end of the body. It is visible only at the moment of extrusion of faecal matter. 2. The endosarc is the more fluid granular protoplasm forming the central portion of the cell-body. a. The food-vacuoles are spherical spaces in the endosarc filled with water containing food- particles. b. The circulation of the endosarc is rendered obvious by the food-vacuoles and the granules, which are carried round in a definite direction. c. The nucleus is an elongated ovoid body near the centre of the cell-body. d. The paranucleus is a much smaller body applied to one side of the nucleus, and resembling it in appearance. In some cases both nucleus and paranucleus appear to be situated in the ectosarc rather than in the endosarc. C. Reproduction. 1. Fission is the most usual method, and is effected in the following manner. A transverse constriction appears on the surface of the animal, and deepens till the body is divided into two, each having a portion of the original nucleus and paranucleus, and each becoming a perfect Paramecium. 2. Conjugation is not a mode of reproduction, but is closely connected with it. Two Paramecia become