Gonad

“ In the most primitive existing Gastropods the gonad opens into the right kidney (Patellidae, Trochidae, Fissurellidae) . The gonaduct, therefore, is derived from the topographically right kidney. The transformation has been actually shown to take place in the development of Paludina. In a dextral Gastropod the shell is coiled in a right-handed spiral from apex to mouth, and the spiral also projects to the right of the median plane of the animal. ”

“ This ventral gonad then develops into the ovary in the female Craniotes, and the testicles in the male.
In the formation of the gonidia or erotic sexual cells and their conjunction at fecundation we have the sole essential features of sexual reproduction; but in the great majority of animals we find other organs taking part in it. The chief of these secondary sexual organs are the gonoducts, which serve to convey the mature sexual cells out of the body, and the copulative organs, which bring the fecundating male sperm into touch with the ovum-bearing female. ”

“ In a majority of cases, however, special ducts are developed, which in the male serve primarily for the escape of the spermatozoa, but secondarily may be associated with intromittent organs. Similarly, in the female, the primary function of the gonad ducts is to provide a passage for the ova, but in many cases they serve also for the reception of spermatozoa, for the development of embryos and for the subsequent exit of the young. ”

“ Gonads and Gonad Ducts.—The Oligochaeta agree with the leeches and differ from most Polychaeta in that they are hermaphrodite. There is no exception to this generalization. The gonads are, moreover, limited and fixed in numbers, and are practically invariably attached to the intersegmental septa, usually to the front septum of a segment, more rarely to the posterior septum. The prevalent number of testes is one pair in the aquatic genera and two pairs in earthworms. ”

“ The ovary or testis is itself a growth from the inner wall of this chamber, which it only partly fills. In Nautilus the right genital duct, which is functional, is a simple continuation to the pore on the postero-dorsal surface of the membranous walls of the capsule in which lies the ovary or the testis, as the case may be. The gonad itself appears to represent a single median or bilateral organ. ”

“ At first, the gland is made up merely of a superficial epithelial layer, and an inner epithelial mass, or epithelial nucleus. In the process of development, large primordial germ cells migrate from the entoderm of the future intestinal canal, and pass through the stalk to the gonad. In the case of the male gonad, seminiferous tubules are very difficult to make out in embryos smaller than 24 millimeters. Then they suddenly differentiate out as solid cords of germ cells, while the connective tissue grows in around them. ”

“ In the vertebrate stock, two main lines of evolution as regards sexual relationships may be traced. The first is predominant in mammals: here, in most species, the female will not receive the male except at fixed times, which are determined by a purely physiological mechanism, the internal secretion of the gonad (reproductive organ) . Here we consequently find that the rule is for the males to fight for the possession of the females, not to display before them. ”

“ In any case, the work on animals definitely shows that, unless the mechanism of activation of instinct by gonad secretion has altered between animal and man more than we have any right to postulate a priori, the quality of gonad secretion and the balance of all the endocrines has to be taken into account far more than is done by the average psycho-analyst. ”

“ But others display signs of sex differentiation that are to be traced back to an awakening interstitial gonad action. Some boys have no interest whatever in sex. Others will show an intense curiosity spontaneously, a curiosity which perhaps may be explained as a larval precocity, dependent upon the minimum of sex hormone production by the gonads. ”

“ In the young embryo a pair of gonads develop that are indifferent or neutral, showing no indication whether they are destined to develop into testes or ovaries. There are also two different duct systems, one of which can develop into the female system of oviducts and related apparatus and the other into the male sperm duct system. As development of the embryo proceeds, either the male or the female reproductive tissue differentiates in the originally neutral gonad of the mammal. ”

“ These cavities are known as the infundibular or subgenital cavities. They serve probably for the aeration of the gonads by admitting to their vicinity water with its dissolved oxygen; they never serve as genital ducts, since the generative products are always dehisced into the stomach and pass out by the mouth. In some genera, for instance, Cyanea and its allies the gonad as a whole protrudes through the subgenital cavity as if it had undergone a hernia, and hangs down in the subumbral space as if suspended by a mesentery (fig. 15) . ”

“ The sense-organs are tentaculocysts which are usually enclosed in vesicles and may be sunk far below the surface. The gonads are on the radial canals or on the stomach (Ptychogastridae) , and each gonad may be divided into two by a longitudinal sub-umbral muscle-tract. The radial canals are four, six, eight or more, and in some genera blindly-ending centripetal canals are present (fig. 26) . The stomach may be drawn out into the manubrium, forming a proboscis (“Magenstiel”) of considerable length. ”

“ The gonads are reduced to a single pair in the adult, although it is possible that they may have a multiple origin in the embryo. Gonoducts for the discharge of the sex-cells are almost invariably present, and may owe their origin either to a change of function on the part of certain kidney-ducts, or to independent evolution from the lining membrane of the coelom. ”

“ The mouth now becomes median and ventral, and is reduced in size, the oral hood (stomodaeum) is formed in front of it, the gill-slits become more numerous and vertically elongated, the endostyle forms along the floor of the pharynx, and the gonads grow as paired pouches from the body-wall. This brings the animal to the young adult condition, reached at a period of probably about three months after the fertilisation of the egg. ”

“ The Gonads or Sex Glands, testes in man, ovaries in woman, affect thru the secretions of their interstitial cells, the pitch of the voice, the growth of pubic hair, the size of the breasts, the distribution of fat.
Good gonads mean masculine looking men and feminine looking women. Poor gonads mean feminine looking men, hairless and with overdeveloped breasts, talking in a high-pitched voice, with a tendency to obesity and laziness (eunuchs) ; scrawny [Pg 232] looking women who may later in life grow abnormally fat, with, in their youth, flat chests, scanty menstruation, etc. ”

“ The vascular system does not readily lend itself to morphological comparison between such widely different animals as Balanoglossus and Amphioxus, and the reader is therefore referred to the memoirs cited at the end of this article for further details.
Reproductive System.—The sexes are separate, and when mature are sometimes distinguished by small differences of colour in the genital region. Both male and female gonads consist of more or less lobulated hollow sacs connected with the epidermis by short ducts. ”

“ Immature males and females are closely alike; the auxiliary and secondary sexual characters almost invariably begin to appear only when the gonads become mature, and fade away when these are injured or destroyed by accident, disease, senescence or artificial interference, and finally, when the activity of the gonads waxes and wanes periodically, there is a corresponding periodicity in the display of the secondary characters. ”

“ The occurrence of male somatic characters on one side or in some part of the body and female on the other, usually associated with the corresponding gonads, has been termed gynandromorphism, and has long been known in insects. ”

“ The number of genital organs varies very much. In the small Amphiura squamata there are two gonads, an ovary and a testis, attached to each bursa, but in the larger species there may be very many more. ”

“ Nussbaum [287] has published the interesting observation that when the Hydras have been well fed the majority become female, when the food supply has been greatly restricted the majority become male, and when the food-supply is moderate in amount the majority become hermaphrodite. The gonads are simply clusters of sexual cells situated in the ectoderm. ”

“ But in the two lowest classes of our stem, the acrania and cyclostoma, they consist merely of simple sexual glands or gonads, the ovaries of the female sex and the testicles (spermaria) of the male; the former provide the ova, the latter the sperm. In the craniota we always find only one pair of gonads; in the amphioxus several pairs, arranged in succession. They must have had the same form in our hypothetical prospondylus (Figures 1.98 and 1.100 s) . These segmental pairs of gonads are the original ventral halves of the coelom-pouches. ”

“ A very early stage in the degeneration is well exemplified by the so-called “meconidium” of Gonothyraea (fig. 41, A) . Here the medusoid, attached by the centre of its ex-umbral surface, has lost its velum and sub-umbral muscles, its sense organs and mouth, though still retaining rudimentary tentacles. The gonads (g) are produced on the manubrium, which has a hollow endodermal axis, termed the spadix (sp.) , in open communication with the coenosarc of the polyp-colony and serving for the nutrition of the generative cells. ”

“ From this an equally slender tube proceeds, which joins its fellow of the opposite side, and the two form a thick, walled tube, which opens on to the exterior within the bursa copulatrix through which the penis protrudes. These two last-mentioned types show features which can be, as it seems, matched in the Eudrilidae.
The gonads develop (O. Bürger) in coelomic spaces close to nephridial funnels, which have, however, no relation to the gonad ducts. The ovaries are solid bodies, of which the outer layer becomes separated from the plug of cells lying within ”

“ Vascular system always present, forming a closed system, more complicated in the larger forms than in the aquatic genera. Several specially large contractile trunks in the anterior segments uniting the dorsal and ventral vessels. Nephridia generally paired, often very numerous in each segment, in the form of long, much-coiled tubes with intracellular lumen. Gonads limited in number of pairs, testes and ovaries always present in the same individual. Special sacs developed from the intersegmental septa lodge the developing ova and sperm. Special gonad ducts always present. ”

“ Such women possess a vigor and energy above the normal, and command responsible positions in society, not only among their own sex, but also among men. They are the ones who, in the present overturn of the traditional sex relationships, will become the professional politicians, bankers, captains of industry, and directors of affairs in general.
THE GONADS (Sexual, Puberty or Interstitial Glands)
The gonads is the name applied to the generative or reproductive glands considered collectively. In the male, they are the testes; in the female, the ovaries. ”

“ Another most important fact is not only that they are fully developed in one sex, absent or rudimentary in the other, but that their development is connected with the functional maturity and activity of the gonads. ”

“ Again, with the longer life of the host, the setting free of the gonads no longer necessitating the destruction of the host, and also the gonads themselves requiring a longer and longer time to be fed up to maturity, the bulk and complexity of the whole organism increased and special supporting structures became a necessity. ”

“ Removal of the reproductive organs or gonads induces, in Man, for instance, if it be effected in youth, the persistence of the childish voice and the non-development of the beard; in the stag the antlers do not appear, and in the cock the comb does not develop perfectly, &c., but we are not yet able to understand clearly why this should be so. ”

“ In the worker castes of these organisms the inhibition of the gonads, except under unusual conditions, is simply prolonged into and throughout adult life. Perhaps in last analysis this inhibition is merely a special manifestation of the extraordinary independence of the insect soma and germ-plasm, as has been so beautifully shown in the castration and transplantation experiments of Oudemans, Meisenheimer, Regen and Kopeć. ”

“ It is becoming ever clearer that the gonads do not operate as independent organs, but in conjunction with the whole of the rest of the endocrine system—thyroid, pituitary, adrenal, and the rest. In the first place, it seems to be established that the [Pg 146] reproductive organs must be in some way activated by other ductless glands before they become normal, just as they in their turn must activate the sexual centres in the brain. This phase of the matter is being investigated by many workers to-day ”

“ But seeing the female sexual organs are pre-eminently the home and breeding place of Venereal disease, this closed what was precisely the most direct way to a correct understanding of maladies of the genitals. The ancient Physicians, like our own forefathers, could at best make leucorrhœa the universal scape-goat; and accordingly even Galen, as we shall find presently, laid no stress on the circumstance, and drew no inference from it, that wherever men were attacked by gonorrhœa, the women with whom they had had coition likewise suffered from the complaint. ”