. Essentials of biology presented in problems. Biology. THE PROTOZOA 191. If it pushes its way past any dense substance in the water, the cell body is seen to change its shape as it squeezes through. The cell body is almost transparent, and consists of semifluid protoplasm which has a granular grayish appearance under the microscope. This protoplasm appears to be bounded by a very delicate membrane through which project numerous delicate threads of protoplasm called cilia. (These are usually invisible under the microscope.) The locomotion of the paramoecium is caused by the movement of these c
. Essentials of biology presented in problems. Biology. THE PROTOZOA 191. If it pushes its way past any dense substance in the water, the cell body is seen to change its shape as it squeezes through. The cell body is almost transparent, and consists of semifluid protoplasm which has a granular grayish appearance under the microscope. This protoplasm appears to be bounded by a very delicate membrane through which project numerous delicate threads of protoplasm called cilia. (These are usually invisible under the microscope.) The locomotion of the paramoecium is caused by the movement of these cilia which lash the water like a multitude of tiny oars. The cilia also send tiny particles of food into a fmmel-like opening, the gullet on one side of the cell. Once within the cell body, the particles of food materials are gathered into little balls within the almost transparent protoplasm. These masses of food seem to be inclosed within a little area containing fluid, called a vacuole. Other vacuoles appear to be clear; these are spaces in Paramoecium which food has been digested. One or two larger vacuoles may be found; these are the contractile vacuoles; their purpose seems to be to pass off waste material from the cell body. This is done by pulsation of the vacuole, which ultimately bursts, pass- ing fluid waste to the outside. Solid wastes are passed out of the cell in somewhat the same manner. The nucleus of the cell is not easily visible in living specimens. In a cell that has been stained it has been found to be a double structure, consisting of one large and one small portion, called respectively the macro- nucleus and the micronucleus. Response to Stimuli. — In the paramoecium, as in the one-celled plants, the protoplasm composing the cell can do certain things. Protoplasm responds, in both plants and animals, to ccTtain agen- cies acting upon it, coming from without; these agencies we call stimuli. Such stimuli may be light, differences of temperature, presence
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1911
