Spermatocyte

“ These enlarged cells are called spermatocytes and form the second stratum. The cells produced by the mitosis of the spermatocytes constitute the third stratum and are called spermatids.
During the transformation of the spermatocyte into a spermatid a reduction of its chromosomes to one-half the number, specific for the species, takes place. ”

“ Usually the two daughter nuclei are formed in an undivided cell. The resting-stage between the two divisions is only partial. The nucleolus appears and divides into two (figs. 33-36) , and the chromosomes change into the dyad form (fig. 36) , in which they come into the second maturation spindle (figs. 37, 38) . The equatorial plate again shows 26 chromosomes (fig. 39) . The formation of the spermatozoa is peculiar in that the original spermatocyte cell-body, as a rule, does not divide; but the four nuclei resulting from the two maturation divisions develop into sperm-heads in one cell. ”

“ Of the dual nature of the spermatids I was very early convinced, because the accessory chromosome is so strikingly displayed by the nuclei in which it exists that it is impossible to overlook its absence in a large proportion of the cells. As to the 199certainty of this partial distribution in the transforming spermatozoa, I am rendered positive by the most careful and painstaking study. This is valuable corroboration of the observed fact that the accessory chromosome remains undivided in one of the spermatocyte mitoses. ”

“ Spermatocytes and spermatids are seen in the more severe types of defective spermatogenesis, and are relatively uncommon, while the more mature forms that result from the transformations of spermatid to adult cell are very often seen. ”

“ Second spermatocyte division—metakinesis.
79. Same; late anaphase. [Pg 23]
[Pg 24]
Plate III. Stenopelmatus.
Fig. 80. Telophase of second maturation mitosis.
81. Young spermatid, showing spindle-remains at s.
82. Spermatid showing a conspicuous chromatin element in nucleus, and spindle-remains (s) elongated.
83. Spermatid, showing centrosome (c) and divided spindle-remains (s and a) .
84. Older spermatid, showing centrosome (c) , axial fiber of tail, and spindle-remains (s) .
85. Spermatid, showing acrosome material (a) migrating to side of nucleus opposite centrosome. ”

“ In some animals it appears that several spermatozoa may normally enter the ovum (some Arthropoda, Selachians, Amphibians and Mammals) , but of these only one forms a male pronucleus (see below) , the rest being absorbed. Gametogeny is the name applied to the formation of the gametes, i.e. of the ova and spermatozoa. The cells of the reproductive glands are the germ cells (oögonia, spermatogonia) . They undergo division and give rise to the progametes, which in the case of the female are sometimes called oöcytes, in the case of the male spermatocytes. ”

“ In the later stages, only a few dividing spermatogonia appear among the debris of the other unrecognizable cells of the tubule. In the epididymis which itself is 42normal, when the testis is showing degeneration, very few spermatozoa appear, in the later stages none. Many spermatids are present in various stages, and some spermatocytes. Animals in the hyper-thymic condition appear to be sterile. ”

“ The human spermatozoon measures about one six-hundredth of an inch in length. It is composed of protoplasm, the substance of which all living creatures are composed. The spermatozoa are believed to be developed from a parent sperm-cell, by the process of segmentation or subdivision, which process is common to all cell-life. The numerous spermatozoa dwell in a gelatinous substance, which, mingling with the other fluidic secretions of the glands of the male, constitutes the male seminal fluid, sperm, or semen, which is ejaculated by the male during the process of copulation. ”

“ The spermatozoön, the principle of life contributed by the male, is so small that it is not visible to the eye except by the aid of a microscope, and, when seen, somewhat resembles a pollywog. These minute centres of life are alive, and move in a fluid which is secreted by the male organs of reproduction, and which is generally called semen. Now, if we study the characteristics of the ovum and of the spermatozoön we may be surprised when we discover some of the same differences which characterize men and women from infancy to old age. ”

“ The male germinal cell is like the female cell in the possession of a nucleus; in other respects it is very different. 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. The human male cell must travel some distance to reach the point where it can meet a ripe and vigorous ovum; and since the journey is not without danger to its life, Nature has provided that exceedingly large numbers of the male cells shall be deposited in the vagina at the time of the marital relation. ”

“ Fecundation results and conception ensues, the ovum then remaining attached to the walls of the Uterus, and in time develops into the foetus. If, however, the ovum is not impregnated, because of absence of copulation or from other causes, it gradually loses its vitality, and is finally cast off with the several uterine secretions.
It should be explained here that the "spermatozoon" of the male (the plural of the term is "spermatozoa") is the male generative "seed." The sperum, semen, or seminal fluid of the male is filled with hundreds of thousands {29}of spermatozoa. ”

“ In the male the testis is a specialized portion of the wall of the genital coelom, and has a structure comparable to that of the ovary. The spermatozoa pass through an orifice from the cavity of the testis to the genital capsule, and thence to the spermiduct. The spermiduct is provided with a glandular pouch, and opens into a terminal reservoir known as Needham’s sac or the spermatophore sac. The function of this pouch is to form the spermatophore, which is an elastic tube formed of structureless secretion and invaginated into itself. ”

“ These defects in spermatogenesis are of course evidenced in the semen by the presence of immature, or abnormal types of sperms. With cessation of spermatogenesis or degeneration of the epithelium of the entire gland, no sperms are formed. Not infrequently one finds numerous tubules, or even the entire testis in which the germinal epithelium is intact, but there is little or no evidence of mitosis, as in some tubules of Bull 6. The cells are several layers deep as in the normal condition, but they are not dividing. ”

“ Many of the spermatozoa, weaker than the others, perish on the way, and only a few continue the journey up through the uterus to the tube. When near the little ovum, which remains passive, their movements become more and more rapid, they seem to be attracted to it as if by a magnet, and finally one spermatozoön—just one—the one that happens to be the strongest or the nearest, makes a mad rush at it with its head, perforates it, and is completely swallowed up by 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. If this explanation is correct, and it is in accord with careful biological observations, it removes from the mother all responsibility for the sex of her child. Furthermore, since the facts indicate that male-producing and female-producing spermatozoa are present in equal numbers, it follows that practically there is an even chance that an embryo will develop into a boy or a girl. ”

“ On the other hand, there is considerable evidence that the ovum has some share in the effect, and if this is so, before any practical results are reached it will be necessary to discover which of two conceivable causes of sex-determination is the true one. It is possible that there are two kinds of ova, as well as two kinds of spermatozoa, and that there is a selective fertilization of such a kind that one kind of spermatozoon only fertilizes one kind of ovum, the second kind of spermatozoon the second kind of ovum. ”

“ The spermatozoon is one of the smallest of known cells, frequently being no more than one hundred thousandth of the size of the ovum, although the extraordinary case of a small Cypris has been recorded in which the spermatozoa are longer than the animal. It is produced in enormous quantities and relatively to other minute cells is extremely tenacious of life. It may retain its vitality in the male organism for a long time after it has become a separate cell, and may exist for lengthy periods in the female organism. ”

“ The germ cells of the woman, though immeasurably less numerous than the male germ cells (the spermatozoa) , yet develop uselessly over and over again in every celibate as well as in every married woman. And myriads of sperm cells are destroyed even in the process of the act which does ensure fertilization of the woman by the single favored spermatozoön. If the theologians really mean what they say, and demand the voluntary effort of complete celibacy from all men, save for the purpose of procreation, this will not achieve their end of preventing the wastage of all potential life ”

“ Now fertilisation does not necessarily occur whenever the male organ comes in contact with the female organ. Fertilisation occurs only when a male-cell (spermatazoon) unites with a female-cell (ovum) ; in other words, when the spermatazoa in the seminal fluid of a man meet and unite with the germ or ovum in the body of a woman. That is the beginning of the child. This union of the two cells need not take place during or immediately after sexual intercourse. It may occur many hours, or even two or three weeks, after connection, because the spermatazoa have motion of their own. ”

“ Seen under a microscope, a single drop of semen reveals a multitude of spermatozoa swimming about in the prostate-carrying medium. It is in this form that the vitalizing male element meets the female infertile ovum. This mass of live and moving germs is poured all around and about the region in which the ovum lies waiting to be fertilized, and every one of them seems to be "rushing about like mad" to find what it is sent to do, namely, to meet and fertilize the ovum. ”

“ In the sperm-cell there occurs just that failure in the production of chromatin which, according to the hypothesis above sketched out, is to be expected; for, in the process of cell-multiplication, the cells which become spermatozoa are left with half the number of chromosomes possessed by preceding cells: there is actually that impoverishment and declining vigour here suggested as the antecedent of fertilization. It needs only to imagine the ovum and the polar body to be alike in size, to see the parallelism ”

“ But nature is lavish where the propagation of the species is concerned. A portion of an ovary or of both ovaries might become diseased, and thousands of ova might become unfit for fertilization; nature therefore puts in an extra reserve supply. We see a still more striking example of this extreme extravagant lavishness in man; only one spermatozoön is necessary to impregnate the ovum, and only one spermatozoön can penetrate the ovum; nevertheless each normal ejaculation of semen contains between a quarter and half a million spermatozoa. ”

“ That of the male is called the spermatozoon (pronounced sper ́ma-to-zoön) . It is sometimes called spermatozoid; the plural is spermatozoa. It is exceedingly small, the smallest of any cell in the body, and has the power to move from place to place. These cells are produced in enormous numbers, and so far as they have been observed under the microscope they differ considerably in power of movement and in perfection of development. Considering their small size, they must make a [163] very long journey to find the ovum; and if they were only few in number, they would rarely succeed ”

“ The cell nucleus is generally situated near the rounded or pointed extremity, with a centrosome immediately behind it, whilst the scanty protoplasm forms the body and vibratile tail; but there appears to be no general significance in the various configurations that occur amongst different animals. The process of spermatogenesis, or production of spermatozoa from the permanent cells of the testis, varies extremely amongst different animals and has been the subject of many elaborate investigations and much confusing nomenclature. ”

“ The Spermatozoan is structurally much different from the ovum, but it also has its nucleus and chromosomes, which carry to the child the transmittable characteristics of the father.
The ovum is usually comparatively large and stationary, and whatever motion is therefore necessary to bring it into contact with the male cell devolves upon the latter, which possesses what is known as a locomotor tail. In addition there are usually many sperms to one ovum, so that the chances are that at least one male cell will reach the egg and effect fertilization, and the beginning of a new life. ”

“ I told you of the germ or ovum that is produced by the ovary of the woman. That ovum of itself could never become a new being. It must be united with a life-giving principle furnished by the man. This principle consists of a fluid in which float tiny little creatures called spermatozoa—one is a spermatozoon. Here is a picture of some. They are too small to be seen without the aid of a microscope. ”