Conjugation (biology)

“ If they are vigorous, then one of the most striking effects of conjugation is to produce some lines that are less vigorous than the original ones, so that they die out. If the animals which enter conjugation are weak, then one of the most striking effects of conjugation is to produce certain combinations that are more vigorous than the original ones, so that they survive, while those that did not conjugate die out. ”

“ In plants, male and female germs, as particles, conjugate or choose one another. In the higher animals male and female bodies conjugate as bodies. This conjugation is accomplished by the mutual choice of the individuals as bodies, and the mutual choice of the individuals as bodies involves the consciousness of both, and this consciousness must have expression, and this expression is language. Hence reproduction in animals is dependent upon the mutual choice of animals, which choice is expressed in language in some form or other. ”

“ Then the two individuals separate and each divides into two. The result of the conjugation, or the coming together, of two individuals with mutual interchange of nuclear substance is to give to the new Paramœcia produced by the conjugating individuals a body which contains part of the body-substance of two distinct individuals. If the two conjugating individuals differ at all—and they always do differ, because no two individual animals, although belonging to the same species, are [Pg 61] exactly alike—the new individual, made up of parts of each of them, will differ slightly from both. ”

“ The theory therefore that conjugation causes a "rejuvenescence and revitalization," without which death must occur, is utterly disproved, as is also the theory that the purpose of conjugation is to maintain the specific average. For here we have unlimited cell-multiplication without any rejuvenescence by means of conjugation, while the specific average is perfectly maintained by the similarity of the conditions to which the different individuals of the species are exposed. ”

“ The two differ in no other respect save that one set has conjugated, while the other has not. What difference is caused by conjugation?
1. We find that the animals which were ready to conjugate, which were actually attempting to do so, are by no means in a depressed, degenerated condition, unable to multiply farther. On the contrary, if they are not allowed to conjugate, each continues to multiply with undiminished vigor. Conjugation is then not necessary for further multiplication. ”

“ The general solution of the problem will, however, be found to lie in the conjugation of unicellular organisms, which forms the precursor of true sexual reproduction. The coalescence of two unicellular individuals which represents the simplest and therefore probably the most primitive form of conjugation, must have some directly beneficial effect upon the species in which it occurs. ”

“ On this subject we can only build hypotheses, but the study of nature shows us that where conjugation ceases reproduction is etiolated and finally disappears, even when it is still possible for a certain time.
From the commencement of life there is thus a powerful law of attraction with the object of reproduction. At first there are unicellular organisms, in which one cell penetrates the other in the act of conjugation. Their substances combine intimately, while the molecules of each nucleus become so arranged as to give the new individual a more fresh and powerful energy of growth. ”

“ We find here already the special and fundamental act of conjugation, that is the fusion of two cells into one, which serves to strengthen reproduction. This act, common to all living things including man, shows us that continuation of life is only possible when from time to time different elements, that is elements which have been exposed to different influences, combine together. ”

“ In the work on artificial parthenogenesis these two functions have been separated experimentally; the initiation of development takes place alone.
Now, in endeavoring to understand conjugation, attention has been given hitherto almost exclusively to the first of these two functions. It was held that the function of conjugation must be to make possible life and development where it was otherwise impossible, just as fertilization arouses the egg to further life and development. But it turns out that conjugation, instead of having this one of the two functions of fertilization, has the other. ”

“ Either the food a, adequate for the animal A, is just as abundant as the food b, suitable for the animal B, and then half the conjugated animal will be nourished by means of the biophors a, the other half by means of the biophors b, and the state of matters is the same as it was before conjugation; or the food b is more abundant than the food a, or conversely, and then the biophors b will have to take the larger share in the nourishment of the conjugate A + B, and they will therefore multiply more rapidly and the biophors a will decrease relatively in number. ”

“ Among protozoa and the lower plants there occur a series of forms of conjugation leading towards the specialized form characteristic of the sexual reproduction of higher animals. The conjugation may be isogamous, that is to say the conjugating cells may be actually or at least apparently indistinguishable. The fusion between the cells may be complete, or may concern only the nuclei. The conjugation may be followed by reproduction, or may apparently have no relation to reproduction. In true sexual reproduction the conjugation is heterogamous, i.e. the gametes are unlike ”

“ As we should expect, the passing from the sexless mode of reproduction to the definite male and female types is not sharply defined or abrupt. Even among many unicellular organisms the process becomes more elaborate with distinct specialisation of reproductive elements. In some cases conjugation is observed, when two individuals coalesce, and each cell and each nucleus divides into two, and each half unites with the half of the other to form a new cell. ”

“ If we examine a little more closely the history of such a "family" of unicellular beings from one period of conjugation to the next, we see that a great number of single individuals, that is, single cells, have proceeded from the double individual formed by conjugation. ”

“ In the simplest forms of conjugation the functions of both parents appear to be identical, but in organisms which are a little more specialized we find male and female reproductive bodies, and the offspring is the result of the union of the male element of one individual with the female element of another; that is, we have true sexual reproduction in its simplest form. ”

“ In order that reproduction may continue without interruption, these writers believe that a rejuvenescence of the living substance is necessary, that the clock-work of reproduction must be wound up afresh; and they recognize such a rejuvenescence in sexual reproduction and in conjugation, or in other words in the fusion of two cells, whether in the form of germ-cells or of two unicellular organisms. ”

“ We have already made ourselves familiar with the process which in unicellular organisms is called conjugation and in multicellular organisms fertilization, and we have seen that its most obvious significance lay in the fact that through it the germ-plasms of two individuals are united. ”

“ As with many of the lowest plants and animals the conjugation of two individuals which are either quite similar or in some degree different, is a common phenomenon, it seems probable, as remarked in the last chapter, that the sexes were primordially separate. The individual which receives the contents of the other, may be called the female ”

“ The germ cell, like the unicellular organism, on conjugating, divides and redivides many times without conjugation ever occurring again among its descendant cells, the successive generations of which may be compared to successive non-conjugating generations of infusorians, so that the body of a multicellular organism in the successive stages of its ontogeny is comparable to later and later generations of infusorians ”

“ In the animal world, into which the moral equation does not really enter, the facts of conjugation represent a simple and natural working-out of functional bodily laws, usually with a seasonal determination. ”

“ Conjugation requires the bringing together of two cells, and consequently the movement of at least one of them. This cellular movement suffices for the lower forms of union and is usually limited to the male cell. Owing to its movement it plays the active role, while the passive role is reserved for the female cell. Hence we see in the higher plants the male cells, or pollen, transported to the pistil by the wind or by insects, and thence reach the egg by mechanical endosmotic attraction which brings about conjugation. ”

“ Conjugation in unicellular animals, in metazoa, binary fission, budding, sporulation, conjugation in chilodon, in monads, hermaphrodites, self-fertilization, in phanerogamous plants, genitals of plants, sex differentiation, erotic chemotropismus in fishes, birds, mammals, attraction of mates, permanent mating, protection of the young, monogamy. ”

“ In those Indian languages where combination is chiefly by agglutination, that is, by the use of affixes, i.e., incorporated particles, certain parts of the conjugation of the verb, especially those which denote gender, number, and person, are effected by the use of article pronouns ”

“ Thereupon conjugation occurs, so that new combinations are produced, adapted to varied conditions, some of which may survive.
Thus it appears to me that the whole series of investigations on old age and on conjugation leads to a unified result, and one that is in most respects in consonance with what we observe in higher animals. But in one respect there is a difference, and this brings us back to the question with which we began. Is death a necessary accompaniment of life? Do the life processes necessarily take such a course that they must lead to death? ”

“ Secondary conjugations are those in which a whole system of forms, like that already described as made from the simple root, is made, with greater or less completeness, from a derivative conjugation-stem ”

“ If we are right in this matter, and we certainly are nearly right, variation must take place for the most part in the germ. These variations may not show until the animal has grown up, but they must have taken place among the determinants in the germ cell or they would not reappear in subsequent generations. ”

“ The fourth, or strong mode of conjugation, which is the most ancient and most flexible of any, comprises five distinct classes of verbs; as, (1) verbs in which the imperf. indicative ends in short a; (2) in long a; (3) in o; (4) in e; (5) in ö. As —
Some verbs may be declined according both to the first and the second form of conjugation ”

“ What Maupas held was that conjugation saves the animals from death, though without increasing their reproductive powers. Richard Hertwig observed, correctly, that conjugation actually decreases the rate of multiplication.
3. A third result of comparing those that have conjugated with those that have not is that many more of the former die or are abnormal than of the latter. In a specially favorable experiment, out of 61 conjugants, eleven lines had died out completely in 33 days, while of 59 lines that had not conjugated, but were otherwise similar, none had died in the same period. ”

“ Yet the evidence of the natural transmutation of species is in one respect much stronger than that of the natural transmutation of languages—in respect, namely, of there being a vastly greater number of cases all bearing testimony to the fact of genetic relationship. ”

“ The conjugation of cells may be viewed as a process quite distinct from reproduction, though it is a necessary preliminary to the long series of cell divisions required to build up the complex bodies of the higher animals and plants. As we descend in the organic scale the conjugating cells become more and more similar to each other and to the so-called vegetative or somatic cells of which the body of the organism is composed. ”

“ The verb stem and a contraction of the necessary pronouns are incorporated, and the words thus formed are used in the conjugation. These are, however, modifications of the affixed particles in the past and future tenses to express differences in time.
In the following conjugation of the verb “to beat” the present tense is given in full. In the past and future tenses, one example in the first person singular is thought sufficient, because any required person and number in each tense can be obtained by following the directions given in the text. ”

“ Owing to the imperfection of language the offspring is termed a new animal, but is in truth a branch or elongation of the parent; since a part of the embryon-animal is, or was, a part of the parent; and therefore in strict language it cannot be said to be entirely new at the time of its production; and therefore it may retain some of the habits of the parent-system. ”

“ It is the germ or seed, so to speak, of animal life; in it is contained all that is necessary for the formation of the perfect living creature; in that little oval case lie snugly packed up, bones, and muscles, and sinews, and all the delicate parts, organs, as they would be called, from a Greek word signifying an instrument, thus the tongue is an organ of speech, the eye of sight, and so on. But all these organs are in an undeveloped state, as the flower is in the bud; develope is a French word, and signifies to unroll, or unfold. The animal is there in embryo ”

“ As the sentence stands, walking modifies rain.
+69. Conjugation.+—The complete and orderly arrangement of the various forms of a verb is termed its conjugation. Complete conjugations will be found in any text-book on English grammar.
The passive voice must not be confused with such a form as the progressive conjugation of the verb. The passive consists of a form of to be and a past participle: [I am instructed] . The progressive tenses combine some form of to be with a present participle: [I am instructing] . ”