This problem reduces itself simply to that of the method whereby the gametes transmit heliotropism to the larvae or to the adult.
For the transmission of this the gametes need not contain anything more than a catalyser or ferment for the synthesis of the photo-sensitive substance in the body of the animal.
In these cases, however, the potential gametes may, failing conjugation, germinate directly, like the zoospores derived from unilocular sporangia.
Or, to express it otherwise, an albino extracted from yellow parents, bred with an albino extracted from black parents, will give an albino offspring whose gametes in equal numbers are bearers of the black and yellow determinants.
Now such a gametic (egg or sperm) constitution can only result when two individuals, all or some of whose gametes are pure with regard to the character albinism, meet in fertilization.
It would seem that in some cases the nuclei of the gametes remain distinct in the zygospore for a considerable time after conjugation.
In this latter case the determinants for black are carried by separate gametes from those carrying grey, and the two kinds of sex-cells exist in approximately equal numbers.
In Zygogonium, although no cell-division takes place, the gametes consist of a portion only of the contents of a cell, and this is regularly the case in Mesocarpaceae, which occupy the highest grade among Conjugatae.
Gametes which fail to conjugate sometimes assume the appearance of zygospores and germinate in due course.
An indefinite but not ultimated number of such generations may follow, but if meanwhile the host is bitten by a mosquito, the parasites develop into gametes in the stomach of the insect.
In Stylorhynchus the difference between the conjugating gametes is not quite so pronounced (fig.
In Stylorhynchus, Leger has shown that the function of the sterile male gametes is to bring about, by their vigorous movements, the melee sexuelle.
In the case of highly-differentiated gametes (Pterocephalus), the actively motile microgametes rush about here and there, and seek out the female elements.
In the forms where the gametes are isogamous or only slightly differentiated and (probably) not of themselves motile, other factors aid in producing the necessary commingling.
Association is very primitive in character and indiscriminate; it takes place indifferently between individuals which will give rise to gametes of the same or opposite sex.
Development of the Gametes and Conjugation in Stylorhynchus longicollis.
This mating is generally regarded as a unifactorial one (producing gametes WM, wM) and to give in every 4 offspring 1 black, 2 blue, and 1 white.
These offspring are, by hypothesis, so far as their gametes go, of two equally numerous sorts, DR and RR.
All were apparently of the zygotic constitution C2J2Nn, forminggametes CJN and CJn.
A hen, of a light buff color spangled with white spots and having a black tail, presumably formed gametes CJnWX, CJnwX, CJNWX, CJNwX.
This was an illustration of the statement that recessives which are supposed to come from two pure recessive gametes show in their soma traces of the dominant type.
Or sterility may be due to pathological causes which prevent the gametesfrom meeting one another in a healthy state.
Mendel affords the strongest of arguments for regarding the nature of the gametes and their relation to the characters of the zygotes in the way that he has done.
And as it takes two gametes to form a zygote, we are in the position of attempting to decide the properties of two unknowns from one known.
The attempt to discover a simple explanation of the nature of sex has led us to assume that certain combinations between gametes are incapable of giving rise to zygotes which can develop further.
The qualities of men and women, physical and mental, depend primarily upon the inherent properties of the gametes which went to their making.
But whether these two bodies exist as such {49} in the gametes or whether in some other form we have as yet no means of deciding.
An individual is said to be homozygous for a given character when it has been formed by two gametes each bearing the character, and all the gametes of a homozygote bear the character in respect of which it is homozygous.
The size of the offspring is affected because the poorly nourished parent offered a bad environment to the young plant, and not because the gametes of the parent were changed through the adverse conditions under which it grew.
He {21} conceived of the gametes as bearers of something capable of giving rise to the characters of the plant, but he regarded any individual gamete as being able to carry one and one only of any alternative pair of characters.
Two such series of gametes coming together must give a generation consisting of x AABB, 2x AABb, and x AAbb, that is, reds and whites in the ratio 3 : 1.
It must be pure for one or the other of such a pair, and this conception of the purity of the gametes is the most essential part of Mendel's theory.
Whenever two similarly constituted gametes unite, whatever the nature of the parents from which they arose, the resulting individual is homozygous in all respects and must consequently breed true.
If it is true, equal numbers of gametes with and without the horned factor must be produced by the F1 ewes, while the factor should be lacking in all the gametes of the hornless F2 rams.
The factors in the gametes of the normal Flat-fish egg cause the normal metamorphosis to take place after the larval symmetry has lasted a certain time.
He has not only studied the chromosomes in the gametes of this fly, and made Mendelian crosses with it, but has obtained numerous mutations, so that his work is a very important contribution to the mutation doctrine.
The evidence concerning sex and sex-linked characters and the localisation of their factors in the chromosomes of the gametes has no bearing on the action of hormones.
In the adult stage activity of the legs produces hormones which influence the same determinants in the gametes to develop legs, but again in the presence of the different hormones which are present in the body generally in the adult stage.
When the division in the gametes of the recessive individual takes place its gametes all contain the recessive character.
There is no universal characteristic of sex except the difference between the gametes and the reproductive organs (gonads) in which they are produced.
We are asked to conceive a quality, or the absence of a factor, in an ovum which is incapable of causing that ovum to be a sperm, but which, when segregated in the gametes descended from that ovum, causes them all to be sperms.
The re-appearance of blue eyes among two of the Scotchman's grandchildren is a clear example of the Mendelian segregation among the gametes of the half-breed Indian mother of the factors which produce blue eyes.
French grandfather had brown eyes, and that, therefore, this colour has segregated out among the gametes of the half-breed Indian mother.
From what we know of analogous cases, there is little doubt that the gametes of his half-breed Indian wife carried the blue or grey factors derived from her French father.
For, in the light of Mendelian researches, it is obvious she was carrying these characters recessive, and that some of her gameteswere pure in respect of them.
In some species of Volvox a still further advance is seen, in that instead of both kinds of gametes being produced in the same colony, the ova may be produced by one colony and the spermatozoa by another.
That is, the segregation is equally likely to be RY/ry giving gametes RY and ry, or Ry/rY giving gametes Ry and rY.
These matings are as follows: Possible couplings Matings of gametes Product 1.
Four Kinds ofGametes in Each Sex Means Sixteen Possible Combinations.
These represent modified pseudopodia, and in the formation of the motile gametes of some of the lower forms, e.
Hence the inference that there is such a splitting of the gametesin the sexual act seems a legitimate one.
When these two sets of gametes meet one another, one of several events may happen.
In this division half of them pass into one daughter cell and half into the other daughter cell, so that, prior to fertilisation both the male and the female gametes contain only half the normal number of chromosomes.
Further, the segregation of the gametes does not appear to be so complete as the above hypothesis requires it to be.
But it may even happen that gametes of individuals of the same species may refuse to coalesce on account of some peculiarity in the composition of one or other of them.
This occurrence points strongly to the conclusion that there were originally many female gametes (cf.
The number of chromosomes of the nucleus of the gamete is therefore reduced, and the divisions by which the gametes arise from the progametes are called reducing (maiotic) divisions.
It is said that in human societies the number of males born increases after wars and famines, but this, if true, is probably due to an affection of the gametes and not of the young zygote.
We thus have a process of "multiple fertilization"; the oosphere really represents a large number of undifferentiated gametes and has been termed a coenogamete.
In all these cases the ascogonium and antheridium contain numerous nuclei; they are to be looked upon as gametangia in which there is no differentiation of gametes, and since they act as single gametes they are termed coenogametes.
Sexual reproduction typical but with sometimes inequality of the fusing gametes (gametangia ?
The cytology of zygospore-formation is not known in detail; the so-called gametes which fuse are multinucleate and are no doubt of the nature of gametangia.
Subsequent proliferation of cells representing certain combinations would then lead to excess of the gametes bearing them.
In these cases certain of the possible combinations of factors occur in the gametic series with special frequency, being in excess, while the gametes representing other combinations are comparatively few.
In the general expressions n is half the number of gametes required to express the whole system.
But nothing can be more certain than that these plants are simply heterozygous combinations made by the union of gametes bearing the characters of diurna and vespertina.
If they were proved to enter from without, like pathogenic organisms, we should have to account for the extraordinary fact that they are distributed with fair constancy to half the gametes of the heterozygote.
The result is that the gametes (sperm and eggs) they respectively produce in maturation are not exactly alike as to chromosome composition.
This statement applies only to the reproductive process, as obviously the male and female gametes contribute equally to the formation of the new individual).
In estivo-autumnal malaria the gametes take distinctive ovoid and crescentic forms, and are not difficult to recognize.
In estivo-autumnal fever usually only the small "ring bodies" and the crescentic and ovoid gametes are seen in the blood.
When a malarious person is bitten by a mosquito, the gametes are taken with the blood into its stomach.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "gametes" in a variety of sentences. We hope that you will now be able to make sentences using this word.
