Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: May 6, 2025
Agassiz calls them Protozoa, Primary Existences. Some divide them into two great classes, namely: the Anthozoa, or Flower-Life; and the Polyzoa, or Many-Life, in which the individuals are associated in numbers.
It seems to rejuvenate the organism so that it is able to go on with its division and thus fulfil its life-mission which is the same for these lowly animals as with the higher, that of perpetuating the species. Classes of Protozoa. The group or Phylum Protozoa is divided into four smaller groups or classes. The amoeba belongs to the lowest of these, the Rhizopoda.
The PROTOZOA. The Protozoa are represented throughout the whole range of geological series, from the Lower Silurian formation to the present day.
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 is yet another of zoophytes, or polyps, and another of sponges, and, finally, we have a sub-kingdom of minute creatures, or animalculæ, of very varied forms, which may make up the sub-kingdom of Protozoa, consisting of animals which are mostly unicellular.
Amoebae were demonstrated in one form of dysentery, and in other tropical diseases protozoa were discovered, so that we were really prepared for the announcement in 1905, by Schaudinn, of the discovery of a protozoan parasite in syphilis.
In the lowest Protozoa, as some of the Rhizopods, we have a homogeneity approaching to that of air, water, or earth; and the ascent to organisms of greater and greater complexity of structure, is an ascent to organisms which are in that respect more strongly contrasted with the relatively structureless masses in the environment. In form again we see the same truth.
We may well wonder: Why did not Laveran simply recognize those sexual forms, and why did he not seek for the period of conjugation in the plasmodia, which were animal micro-organisms? If he had borne in mind the complete cycle of the protozoa, he would have recognized them.
In studying protozoa we noticed that they reproduced by fission, each adult individual dividing into two young ones. There is therefore no old parent left to die. Natural death does not occur here, only death by violence or unfavorable conditions. The protozoa are immortal, not in the sense of the endless persistence of the individual, but of the absence of death.
There must be permanent pores in the membrane to receive food or let out rays of the living substance to act as oars or arms. Thus we get an immense variety amongst these Protozoa, as the one-celled animals are called. Some have a definite mouth-funnel, but no stomach, and cilia drawing the water into it.
Word Of The Day
Others Looking