While agreeing with Cienkowski as to the parasitic nature of the yellow cells of Radiolarians, he holds strongly that those of anemones and jelly-fishes are unicellular glands.
The low unicellular organisms are potentially immortal, the higher multicellular forms with well-differentiated organs contain the germs of death within themselves.
The phenomenon of old age is not evident in the case of the unicellular organism reproducing by fission.
These simplest forms multiply or reproduce by fission, but such asexual reproduction is almost entirely confined to the unicellular forms of life.
From one or more simple primitive unicellular forms have arisen the great multitude of multicellular forms that now exist.
Even the external motions of a unicellular organism--of an amoeba, at any rate--are sometimes explained mechanically.
The reproduction ofunicellular organisms consists in just this--the living being divides into two halves, of which each is a complete individual.
This study of germination leads also to a very definite conclusion with regard to the genus Uromyces--that it is much more closely related to Puccinia and its immediate allies than to other unicellular Uredines.
With it is associated an unicellular yellow Uredine, of which it is a condition.
The elementary memory of the unicellular protist is made up of the molecular memory of the plastidules or micellae, of which its living cell-body is constructed.
Indeed, we have found in the great cell-nucleus (meganucleus) of the infusoria a central organ of psychic activity, which plays much the same part in their unicellular organism as the brain does in the psychic life of higher animals.
The organism of the metazoon, on the contrary, is only unicellular at the commencement, and is subsequently built up of a number of cells which form tissues.
We learn the character of the psychic activity of these unicellular organisms from the comparative physiology of the protists of to-day.
As this cell has a "soul" from the commencement, so had also the corresponding unicellular ancestral forms, which were represented in the oldest series of man's ancestors by a number of different protozoa.
The automatic and the reflex movements which we observe everywhere, even in the unicellular protists, seem to be the outcome of inclinations which are inseparably connected with the very idea of life.
In this sense the unicellular protophyta and protozoa are throughout life physiological individuals, just as much as the multicellular tissue-plants and animals.
These living cells possess a certain sum of physiological properties to which we give the title of the "cell-soul," just as we do in the permanently unicellular protist (see p.
Extremely simple unicellular animals, however, are known to date from early times.
If theunicellular individuals are differently modified, however slightly, then, whenever conjugation occurs between two such individuals, there will be a commingling or combination of the different characters.
We have just seen the nature of reproduction in the simple unicellular am[oe]ba.
It is sufficient to state that unicellular plants are spoken of as protophyta, and unicellular animals as protozoa, the whole group of unicellular organisms being classed together as protista.
It can only arise in the lowest unicellular organisms.
I have repeatedly spoken of immortality, first of the unicellular organism, and secondly of the reproductive cell.
Footnote 66: The conception of Protozoa and Metazoa does not correspond exactly with that of unicellular and multicellular beings, for which Götte has proposed the names Mono- and Polyplastides.
If this were not so, unicellular beings must also have been endowed with natural death.
I imagine that I have now sufficiently explained the above proposition, that the repetition of the phylogeny in the ontogeny does not and cannot occur among unicellular organisms.
The fundamental biogenetic law applies only to multicellular beings; it does not apply to unicellular forms of life.
The origin of hereditary individual variability cannot indeed be found in the higher organisms—the Metazoa and Metaphyta; but it is to be sought for in the lowest—the unicellular organisms.
In fact, I believe I have definitely shown that no process exists among unicellular animals which is at all comparable with the natural death of the higher organisms.
The unicellular nature of Gregarines was first realized by A.
The nucleus remains single, so that there is no question as to the unicellular or individual nature of the entire animal.
That these unicellular ancestral forms did once exist follows directly from the phenomena which we perceive every day in the fertilised ovum.
The only exception is found in the protozoa, the very lowest and simplest forms of animal life; these remain unicellular throughout life.
This inference from the unicellular embryonic form to the unicellular ancestor is so simple, but so important, that we cannot sufficiently emphasise it.
On the other hand, many cells attain a considerable size, and run occasionally to several inches in diameter, as do certain kinds of rhizopods among the unicellular protists (such as the radiolaria and thalamophora).
We must, therefore, turn next to the question whether there are to-day any unicellular organisms, from the features of which we may draw some approximate conclusion as to the unicellular ancestors of the multicellular organisms.
There are independent unicellular organisms of the simplest character which develop no further, but reproduce themselves as such, without any further growth.
Yes, and as such may be classed the drops of life known as unicellular organisms.
Certain of the lowest unicellular forms might indeed have persisted, for when dormant they can stand great extremes of dry heat and of cold for a long time.
In certain hot springs, some of the lowest unicellular plant forms exist in water which is only a little below the boiling point.
Cell-division is probably only a special case of a process similar to that by which the pattern of the skeleton is laid down in a unicellular body such as that of a Radiolarian or Foraminiferan.
In the reproduction of unicellular organisms and many other cases, the products formed at the two poles are, so far as we can tell, identical.
It is convenient to restrict the term symbiosis to complementary partnerships such as exist between algoid and fungoid elements in lichens, or between unicellular algæ and Radiolarians,[45] or between bacteria and higher plants.
As we have seen, for a considerable period of time after their first detection these unicellular organisms were considered to be members of the animal kingdom.
Alga-like fungi with unicellular thallus and well-marked sexual organs.
The basidium is a unicellular or multicellular structure from which four basidiospores arise as outgrowths; it starts as a binucleate structure, but soon, like the ascus, becomes uninucleate by the fusion of the two nuclei.
The protoplasm then becomes cut up by a series of clefts into a number of smaller and smaller pieces which are unicellular in Pilobolus, multicellular in Sporodinia.
They are characterized by their unicellular nature, their power of rapid budding, their capacity for fermenting various sugars, and their power of forming endogenous spores.
The whole of these lower creatures, therefore, may be spoken of as unicellular organisms; as though they may consist of many cells, those cells retain their individuality.
Thus, a unicellularplant may take on a great complexity of form while still remaining purely unicellular.
Other instances of the coherence of the cells of unicellular organisms into indefinite and inconstant aggregations is presented by some radiolarians, individuals which cohere into what are called colonies.
We have seen that unicellular organisms may unite into a cylindrical or spheroidal colony, as in some Radiolaria, or into a spheroid of closely-adjusted cells, forming one layer, as in Volvox.
The spores, with few exceptions, are unicellular when shed, and may develop at once or after a resting period.
The unicellular spores when supplied with moisture germinate (fig.
It is equally certain that these unicellular plants and animals are themselves only the specialized descendants of common ancestors--unspecialized unicellular organisms which are neither strictly vegetable nor animal.
All the leaves contained unicellular and other Algae, still of a greenish colour, which had evidently lived as intruders, in the same manner as occurs, according to Cohn, within the leaves of this plant in Germany.
In this bladder, as well as in several others, there were some unicellular Algae, and one multicellular Alga, which no doubt had lived as intruders.
They are supported on elongated, unicellular pedicels (containing a nucleus with a nucleolus) which rest on slight prominences.
I could detect no sessile glands; nor would these have been of any use, as the upper surface of the leaves is thickly clothed with pointed, unicellularhairs directed upwards.
As no instance is known of unicellular structures having any power of movement,* Byblis, no doubt, catches insects solely by the aid of its viscid secretion.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "unicellular" in a variety of sentences. We hope that you will now be able to make sentences using this word. Other words: unicameral; unicellular; unidirectional; unilateral; univocal
