United States or Tonga ? Vote for the TOP Country of the Week !
Had it done no more than give to Protozoa and Protophyta that cell-form which characterizes them had it done no more than entail the cellular composition which is so remarkable a trait of Metazoa and Metaphyta had it done no more than cause the repetition in all visible animals and plants of that primary differentiation of outer from inner which it first wrought in animals and plants invisible to the naked eye; it would have done much towards giving to organisms of all kinds certain leading traits.
There are "blastaeads" of this kind even among the Protophyta the familiar Volvocina, formerly classed with the infusoria. The common Volvox globator is found in the ponds in the spring a small, green, gelatinous globule, swimming about by means of the stroke of its lashes, which rise in pairs from the cells on its surface.
They belong to various groups both of the Protophyta and Protozoa. To have some idea of those ancestors of our race that succeeded phylogenetically to the Moraeada, we have only to follow the further embryonic development of the morula. In this way the solid mulberry-embryo becomes a hollow sphere, the wall of which is composed of a single layer of cells.
Though solar and stellar systems amaze by their grandeur of scale, yet is true manhood the maximum of Nature; though microscopic and sub-microscopic protophyta amaze by their inconceivable littleness, yet is mock manhood Nature's minimum. The latter is the only negative quantity known to Nature; the former the only revelation of her entire heart.
With but few exceptions, and those only partial ones, the lowest animal and vegetal forms are inhabitants of the water; and water is almost their sole constituent. Dessicated Protophyta and Protozoa shrink into mere dust; and among the acalephes we find but a few grains of solid matter to a pound of water.
The Chromacea build up their plasm directly from inorganic matter; the Bacteria feed on organic matter. Hence, if we logically divide the protist kingdom into plasma-forming Protophyta and plasma-consuming Protozoa, we must class the Bacteria with the latter; it is quite illogical to describe them as is still often done as Schizomycetes, and class them with the true fungi.
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.
So again, the Infusoria possess all the characters of animality, but it can hardly be said that they are as clearly allied to the worms as they are to the Noctilucae. On the whole, it appears to me to be most convenient to adhere to the old plan of calling such of these low forms as are more animal in habit, Protozoa, and such as are more vegetal, Protophyta.
Sexual conjugation thus remains a process which is radically the same as the non-sexual mode of propagation which preceded it. The fusion of the nuclei of the two cells was regarded by Van Beneden, who in 1875 first accurately described it, as a process of conjugation comparable to that of the protozoa and the protophyta.
"To this one can only reply that we know for a certainty that even very highly-organized animals do continue to live at a depth of 300 and 400 fathoms, inasmuch as they have been dredged up thence; and that the difference in the amount of light and heat at 400 and at 2,000 fathoms is probably, so to speak, very far less than the difference in complexity of organisation between these animals and the humbler Protozoa and Protophyta of the deep-sea soundings.
Word Of The Day