Picture - Cosmic Polymath

AMCEBA PROTEUS 333
The amcsba draws in its pseudopodia and assumes a spherical shape at a temperature of 35' C. If the
temperature be raised to 40° C. it dies. Under unfavourable circumstances, such as drought, the ectoplasm secretes
a thin hyaline case, and the amcEba becomes encysted and dormant, in which condition it is carried by the wind or
other means to various localities.
The amoeba is invested with practically universal powers, and furnishes one of the most remarkable examples
known of the potentialities residing in rudimentary living matter. Thus any part of its substance may become a
stomach and digest its food, and any part of its body may throw off the waste products ; it has, however, neither
mouth nor anus. It feeds upon diatoms, desmids, spores of algas, and other vegetable matter, and occasionally on
animal matter, such as portions of rotifers and of Protozoa, notably Arcella.
When the amoeba falls in with a microscopic alga or food particle, the protoplasm flows round it ; the ectoplasm
opening to receive it and closing behind it. It enters the endoplasm with a drop of water which constitutes the
food-vacuole, and is temporarily included in the body of the amoeba. The alga is slowly digested, its insoluble
proteids being converted into soluble and diffusible proteids, which pass into the substance of the endoplasm. It
Fig. 68.
Fig. 68. Ama'ha pwteux as seen under varying conditions of size and shape (A to J), magnified from 400 to 800 diameters
(after Masterman, and Marshall and Hurst).
A. Amoeba in the encysted state, composed mainly of granular and clear sarcode ; c, contractile vesicle ; d, nucleus. It contains
an oval-shaped diatom.
B to J. Different shapes assumed by larger and smaller amoeba. In these figures the contractile vesicle is seen at c, the
nucleus at d, and the finger-like projections at e. The projections, sometimes designated pseudopodia, are for the most part
conicalin shape, as seen at C, D, E, F, G, H, and 1. They are caused by the animal voluntarily forging a part of its body outwards
from the centre centrifugally. They are retracted in an opposite direction or centripetally. They are not due to contractions ; if
they were, the projections would not be conical-shaped, but constricted where united to the body. In reality, they are produced
by an aggressive, streaming, rhythmic movement similar to what occurs in the plasmodium of the Mycetozoa and gromia already
described.
At E, the body (a) of an amoeba is stretched over a large diatom (//).
At J, the varying forms assumed by a small amoeba, at intervals of half-a-minute, are given.
may be well to state that the proteids are themselves constituents of protoplasm. The amoeba, it is believed, cannot
digest carbo-hydrates or fats, and does not build up its protoplasm from lower chemical constituents. The
indigestible cellulose walls of alga and other intractable materials are extruded from the body. The amoeba
inhales oxygen and exhales carbonic acid, in which respect it resembles the higher animal forms. It has, however,
no branchiae, gills, or lungs ; its whole substance performing this important function.
The reproduction of the amoeba is effected in the simplest manner possible. The nucleus, and with it the
sarcode of the body, divides into two. In this respect the process resembles the first step in the segmentation of
the impregnated ovum of the higher animals. There are, however (so far as known), no male and female elements,
and the animal is not hermaphrodite. The original individual becomes two separate entities, each of which, after
a short time, becomes as perfect as the parent, and so hfe is transmitted and continued in the most direct and effective
manner. The reproduction of the amoeba is fundamental and thorough-going. It does not require two separate
organs or individuals for its consummation. It is thought by some that the amoeba has not only the power of
dividing into two by binary fission, but that two amoebae can come together, coalesce, and conjugate to form one
individual. The process of conjugation, while not quite made out in the amoeba, certainly occurs in other low animal
forms, such as the Gregarines and Infusoria. The powers inhering in what is practically undifferentiated living
matter are at once striking and impressive. They bring us face to face with the eternal verities of matter and