In the history of the male element or spermatozoon, there is an analogous reduction, so that when spermatozoon and ovum unite in fertilisation the normal number is restored.
We are not at present concerned with the precise number of determinants, but we can see no reason why a spermatozoon should not contain millions if they were needed.
Each spermatid transforms into a mature spermatozoon (f).
Thus normally only one spermatozoon unites with an egg.
And it is a very significant fact that while the ovum and spermatozoon are very unequal in size themselves, the chromosomes of the two germ-cells are of the same size and number.
And the bulk of the nucleus in the spermatozoon consists of the chromosomes or their products.
There is a soul even in the maternal ovum and the paternal spermatozoon (cf.
Even in the ninth month, when most of the organs of the human embryo are formed and arranged as they appear later, there is no more trace of mind in its psychic life than in the ovum and spermatozoon from which it was evolved.
And now occurs the chief phenomenon of fertilisation: the nucleus of the spermatozoon unites with the nucleus of the egg.
The almost spherical egg of our Echinus only measures about a tenth of a millimetre in diameter; and the head of the spermatozoon has a volume which is only the four-hundred-thousandth part of the volume of the egg!
By fertilisation proper we understand the joining of the male element, the spermatozoon or the spermia, with the female element, the egg.
The hereditary masses contained in the egg and spermatozoon can be composed only of such particles as are the bearers of cell-characters.
In other cases, the alien spermatozoon may penetrate the egg and unite with its nucleus, making, however, an unsatisfactory combination in various degrees of infertility.
But the ovum that is successful finally arrives at the Uterus where it awaits impregnation or fertilization by the spermatozoon of the male.
But wherever the actual contact of spermatozoon and ovum occurs, the blending of the elements is performed and fertilization, impregnation, or fecundation is accomplished.
Doncaster says "The general conclusion with regard to man must therefore be that if sex is determined solely by the spermatozoon there is no hope either of influencing or predicting it in special cases.
Each spermatozoon is a minute living, moving creature, resembling a microscopic tadpole.
As a result of copulation, then, the spermatozoon (or a number of spermatozoa) comes in contact with the female ovum or egg.
The successful spermatozoon then loses its tail, and the remaining head and body become what is known as "the male pronucleus.
The human spermatozoon measures about one six-hundredth of an inch in length.
See Ovum and Spermatozoon Reptiles, love amongst, 79 Responsibility in the sexual relationships.
Thus it seems that either the egg or the spermatozoon of the sea-urchin contains all the essential elements for the production of the perfect larva of a daughter organism.
They point out that the spermatozoonis a small intensely active body, which dissipates its energy in motion, while the ovum is a large inert body--the result of the female tendency to conserve energy and to build up material.
Conversely, Loeb showed that the nucleus of the spermatozoon can be dispensed with.
In the spermatozoon the dissipated energy appears in the form of active movement; in the adult organism it takes the shape of plumes and other ornaments, of song and contests for the females.
We have seen that the spermatozoon represents the solitary contribution of the father toward the development of the child, and the spermatozoon, therefore, must convey the material basis of paternal inheritance.
Longer but much narrower than the ovum, the tiny arrow-shaped spermatozoon is particularly distinguished by its active motility, for it has a tail that propels it.
Since only one spermatozoon enters the ovum, whether or not the child will be a boy or a girl depends entirely upon which type gains entrance.
In man, for example, the addition of twenty-four chromosomes from the spermatozoon to an ovum that already contained twenty-four chromosomes of its own would mean that after fertilization the ovum contained forty-eight.
Although the identity of the spermatozoon is lost at the moment of fertilization, its influence just then begins to be asserted.
Almost at the moment when they touch, the two cells unite so intimately that all trace of the spermatozoon is lost.
But the other variety, represented by the Spermatozoon and developed only in the male sex, is also required for the production of a human being.
On the other hand, single ovum, or identical, twins are always of the same sex; this follows, since but one egg and but one spermatozoon are here concerned.
We may conclude from the fact of a single spermatozoon or pollen-grain being insufficient for impregnation, that a certain number of gemmules derived from each cell or unit are required for the development of each part.
Most of the earlier observers thought that the spermatozoon did not penetrate into the ovum.
The lively spermatozoon travels towards the ovum by its serpentine movements, and bores its way into the female cell (Figure 1.
It bears in the cell and nuclear matter of the penetrating spermatozoon a part of the father's body, and in the protoplasm and caryoplasm of the ovum a part of the mother's body.
The older theories of impregnation generally went astray in regarding the large ovum as the sole base of the new organism, and only ascribed to the spermatozoon the work of stimulating and originating its development.
Hence, every spermatozoon was regarded as a homunculus, a tiny complete man; all the parts were believed to be pre-formed in it, and merely grew larger when it reached its proper medium in the female ovum.
In the previous illustrations we have distinguished in the spermatozoon a head, trunk, and tail.
It is the latter alone that combines in conception with the invading nucleus of the fertilising spermatozoon (the pronucleus masculinus).
The spermatozoon then bores its way into this with its head, the tail outside wriggling about all the time (Figure 1.
A single human spermatozoon magnified 2000 times; a shows it from the broader and b from the narrower side.
The fertilisation of the ovum by the spermatozoon (of a mammal).
Sexual reproduction offers an infinite variety of interesting forms in the different classes of animals and plants, especially as regards the mode of conception, and the conveyance of the spermatozoon to the ovum.
This tiny round corpuscle of chromatin now acts as a centre of attraction for the invading spermatozoon in the large ripe ovum, and coalesces with its "head," the male pro-nucleus.
The spermatozoon is also like that of other animals, consisting of a rounded head and a lash-like tail, the movements of which enable it to move rapidly through the water.
The egg of Hydra is said to be fertilized as it lies at the base of the ectoderm, through which the fertilizing spermatozoon bores its way.
Yet the fact remained that all efforts to develop the spermatozoonalone (without the agency of any egg material at all) into an individual had signally failed.
Neither the ovum nor the spermatozoon (the human race is referred to) is capable alone of developing into a new individual.
Loeuwenhoek's development of the microscope in the 17th century led immediately to the discovery of the spermatozoon by one of his students.
This small nucleus of the spermatozoon penetrates the covering membrane of the ovum, enlarges, and becomes the male pronucleus.
As the nucleus of the spermatozoon is too small to carry the spirochete of syphilis, the infection is through the semen in a manner not yet clear to us.
The germinal vesicle that supposedly splits into two is not fecundated by two spermatozoa, they say, because where there is only one nucleus in the beginning, the entrance of a second spermatozoon commonly kills the ovum.
The spermatozoon is a ciliated cell with the power of locomotion, through the movement of the tail of the cell.
If the body-cell has, say, twenty-four chromosomes, the spermatozoon of the animal or plant from which the cells are taken will have twelve chromosomes and the ovum will have twelve.
Fecundation usually occurs after a menstruation, but not necessarily so; the spermatozoon may live in the tube for seventeen days awaiting the ovum.
The reduction-division in both ovum and spermatozoon is in reality far more complicated than the broad summary given here.
As soon as the ovum breaks through the surface of the ovary it has all the qualities of the spermatozoon except locomotion.
In oogenesis and spermatogenesis the phases of "Reduction," wherein the ovum and spermatozoon get rid of half the chromosomes during the stages of maturation of these germ-cells, are somewhat similar for both sexes.
Impregnation is effected by the entrance of the head of a single spermatozoon (the tail remaining outside) through the micropyle, and then along the column of clear protoplasm to the female pronucleus.
The head of the spermatozoon on entering the egg becomes enveloped by the superficial protoplasm, and travels inward with its envelope, while the tail remains outside.
It shows the prominence of the ovum through which the spermatozoon has entered.
A prominence, pointing towards the nearest spermatozoon, now arises from the superficial layer of protoplasm of the egg and grows till it comes in contact with the spermatozoon (Figs.
At the point where the spermatozoon entered a crater-like opening is left in the membrane (Fig.
At whatever point of the egg the spermatozoon may have entered, it gradually travels towards the female pronucleus.
Each spermatozoon forms a separate pronucleus with a surrounding sun; and several male pronuclei usually fuse with the female pronucleus.
The spermatozoon first makes its way through the mucous envelope of the egg, within which it swims about, and then bores with its head into the polar prominence.
Portion of the ovum of Asterias glacialis after the entrance of a spermatozoon into the ovum.
Conversion of the head of the spermatozoon into a nucleus--the male pronucleus.
The head of the spermatozoon when in the egg forms a nucleus for which the name male pronucleus may be conveniently adopted.
When an ovum Fg is fertilised by a spermatozoon fG, the resulting zygote, FfGg, is heterozygous for both F and G, and in appearance is a female grossulariata.
The zygote resulting from the fertilisation of an ovum fg by a spermatozoon fG is heterozygous for G, but does not contain F, and therefore is a male grossulariata.
When this happens an ovum of any one of the four types has an equal chance of being fertilised by a spermatozoon of any one of the four types.
We are led, therefore, to suppose that an ovum carrying the yellow factor is unproductive if fertilised by a spermatozoon which also bears this factor.
Spermatocytes of Bombyx mori, showing the precocious appearance of the spermatozoon flagellum and its relation to the centrosome.
In all cases, however, whether we examine the free-living shapeless and slowly creeping Amoeba, or the striped muscle cell or spermatozoon of the Metazoa (fig.
The centrosome introduced by the spermatozoon has divided into two centrosomes, one at each pole of the nucleus.
An acrosome develops at the anterior end, the head condenses and lengthens, and we have the ripespermatozoon (fig.
The mature spermatozoon with its forked anterior end appears in figure 93.
The human spermatozoon is only fifty-four thousandths of a millimetre in length, and from forty-one to fifty-three thousandths of a millimetre are taken up by its flagellum.
The human spermatozoon consists of a flattened head which has a thin protoplasmic cap extending down two-thirds of its length.
In the human spermatozoon the head is ovoid, appearing pear-shaped or pointed in one view and elliptical in another.
If they be examined under the microscope as a part of a normal nocturnal emission, they will be found to be almost motionless or very greatly lacking in typicalspermatozoon activity.
The spermatozoon is about 1/20 of an inch in length and consists of a head, body and a vibratile tail.
They represent the male reproductive cells, which during coitus are introduced into the interior of the female reproductive organs; a single spermatozoon unites with the ovum of the female to form the fertilised ovum.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "spermatozoon" in a variety of sentences. We hope that you will now be able to make sentences using this word.
