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Updated: May 6, 2025
The fertilized egg-cell, formed by the union of egg and spermatozoon, is a single cell, like the individual resulting from the conjugation or fusion of two protozoa. But in the many-celled individual, which develops out of the fertilized egg, there are two kinds of cells. 1.
Though in those microscopic Protophyta and Protozoa inhabiting the water the spores of algæ, the gemmules of sponges, and the infusoria generally we see locomotion produced by ciliary action; yet this locomotion, while rapid relatively to their sizes, is absolutely slow.
In all the higher Protozoa, as also in the Protophyta, we meet with a fundamental differentiation into cell-membrane and cell-contents, answering to that fundamental contrast of conditions implied by the words outside and inside.
It is, of course, most important for every farmer to know the soil and whatever may grow on it and feed on it. All the new discoveries as to the power of phosphates to increase the crop or as to the part which protozoa play in the inhibition of fertility, or the influence of parasites on the enemies of the crops and the numberless naturalistic details of this type, are certainly most important.
Both make evolution a creative and a continuous process. Bergson lays the emphasis upon the cosmic spirit interacting with matter. Professor Moore philosophizes as truly as does Bergson when he says "there must exist a whole world of living creatures which the microscope has never shown us, leading up to the bacteria and the protozoa.
Like these unicellular Protozoa, the colourless blood-cells creep slowly about, their unshapely plasma-body constantly changing its form, and stretching out finger-like processes first in one direction, then another. Like the Amoebae, they take particles into their cell-body.
But after the first stupefaction, when men were convinced of the facts, there was an outcry from all the intelligent: How was it possible that we did not find it out before? Was not the cycle of the protozoa a well-known fact? Did not every one declare that the system of circulation was closed and impervious to micro-organisms?
Let us begin with the Protozoa, or one-celled forms the lowest form of animal life. The lowest form of this lowest class is that remarkable creature that we have mentioned in previous lessons the Moneron. This creature lives in water, the natural element in which organic life is believed to have had its beginning.
In the second place, the vital struggle includes the battles of every species with other kinds of living things whose interests are in opposition. The relations of protozoa and bacteria, conger-eels and other fish, English sparrows and hawks, plants and herbivorous animals, are typical examples of the universal conflict in which all organisms are involved in some way.
Among the Protozoa referred to in one of the earlier chapters mention was made of certain trypanosomes which inhabit the blood of man and certain animals. Very little was known concerning these parasites previous to the beginning of the present century, but since that time several have been found to be of great economic importance.
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