THE CONTRACTILE VACUOLE IN AMOEBA PROTEUS (LEIDY)

¹ From the Zoölogical Laboratory of the Johns Hopkins University and the Marine Biological Laboratory, Woods Hole, Mass.

1. The contractile vacuole in Amoeba proteus contains at the surface a well differentiated membrane about 0.5µ thick. Adjoining this membrane on the outside there is usually a layer of substance in which numerous beta granules (Metcalf's "excretory granules") are imbedded. This layer is more viscous and heavier than the adjoining cytoplasm. It is usually about 3µ thick when the vacuole is maximum in size and it becomes thicker during contraction.

2. The beta granules around the contractile vacuole vary greatly in number and the layer of substance in which they are imbedded varies greatly in thickness, without any apparent variation in the function of the vacuole. These facts indicate that neither the granules nor the layer of substance is involved in the function of the contractile vacuole, at least not directly.

3. The differentiation of a layer of substance on the surface of the contractile vacuole is probably due to the action of the fluid in the vacuole on the adjoining cytoplasm.

4. There is much confusion concerning the ideas held by different investigators in regard to the nomenclature, the structure and the function of the various granules and crystals in the cytoplasm of the protozoa.

5. Bütschli's "Excretkörnchen" consist of various different kinds of granules and crystals found in protozoa. Schewiakoff's "Exkretkörner" are optically active bodies, nearly all of which, if not all, are crystals. Metcalf's "excretory granules" are not optically active. They are approximately 1µ in diameter and have staining properties like the mitochondria in other cells. The "Excretkörnchen of Bütschli, the "Exkretkörner of Schewiakoff and the "excretory granules" of Metcalf therefore differ radically in structure.

6. Bütschli says the "Excretkörnchen" re end products of metabolism but he says nothing concerning their elimination. Schewiakoff contends that the "Exkretkörner" are formed in the food vacuoles, pass out into the cytoplasm, dissolve there and are eliminated by the contractile vacuole. Metcalf holds that the "excretory granules" (Mast's beta granules) are permanent structures which function in excretion of substance by the contractile vacuole. Mast and Doyle maintain that they function in transporting substance through the cytoplasm.