Page:The New International Encyclopædia 1st ed. v. 18.djvu/40

* SEWING MACHINE. ae SEX. United fitatcii, vol. x., part iv., "ilaiiufactures" (Washington, 1902) ; Byrii, I'rogress of Invention in the Mncteenth Century (New York, 1900). SEX (OF. aexe. from Lat. sexiis, seens, sex, from secare, to cut ; connected with OHG. saga, sega, Ger. Huge, AS. saga, Eng. saw) (in ani- mals). The capacity, in all Init the lowest organ- isms, of each individual producing either eggs or sperm cells (or both), i.e. germ cells which ai-e either female or male. In the lowest or uni- cellular animals, reproduction (q.v.) is by self- division or by germs, which so far as we know are devoid of sexuality; such forms are said to be 'asexual.' The next' step, one suggesting sex- ual reproduction, is the phenomenon of conjuga- tion. In all animals from sponges to man re- production is by male and female cells. The ovary and testis are se.xual glands (go- nads), and may be regarded as the primary sexual organs. In nearly all animals, from the flatworms to man, there is a passage or outlet for the expulsion of the sexual products, and accessory organs for the dilution and expulsion of the seminal fluid, or for secreting the egg- shell: also external appendages of less or greater complexity in those forms which pair; and egg- laying organs, as the ovipositors of insects, brood-pouches, and dift'erent forms of uteri. Judg- ing by the lowest forms, animals were probably at first hermaphroditic, growing out of a uni- sexual condition. Hermaphroditism is a condi- tion in which both male and female organs are developed in the same individual. There are two kinds of hermaphroditism, the true and the spu- rious; in the former the germ glands contain both male and female germ cells; in the latter the accessory organs are of an ambiguous char- acter. Hermaphroditism is normal in some spe- cies and abnormal in others. Spurious her- maphroditism is met with in all dia>cious groups. In insects it has been repeatedly noticed. Thus one wing may have the male coloration and the one on the opposite side female coloration ; or the anterior and posterior parts of the animal may have opposite secondary sexual characters; or the sexual characters may be intermingled, or, more rarely, blended. Among vertebrates abnormal hermaphroditism is rare. Fishes have, however, been described with an ovary on one side and a testis on the other, and birds have been repeatedly described with ambiguous secondary characters. These phenomena usually appear late in life, but they may occur in young birds, which are then usually sterile. A similar tendency to gain characters of opposite sex is seen in old persons, in whom the germ glands are no longer functional. Con- cerning the interpretation of abnormal her- maphroditism it may be said that at an early stage of development all animals are sexless, but their germ glands seem to possess the poten- tiality of both sexes; typically, in dicecious or- ganisms only one of these potentialities is real- ized, but exceptionally both of them may be to a greater or less complete degree. Origin of Sex. This is an unsettled problem. We do not understand how, from being at first hermaphroditic or asexual, as was probably the case, the male and female characteristics became gradually established. What in the higher ani- mals determines sex is also an unsolved problem. Hundreds of theories have been proposed as to the epoch at which the sex of the embryo is finally determined. Food or nutrition is as im- poitant a factor as any in determining what the sex of the future animal may be. Certain ex- periments throw light on the subject in the case of animals. Yung divided a batch of tadpoles into three lots, the proportion being 54.4li, 01.39, and odAi. The average number of females was thus about 37 in lOU. In the first brood b}' feeding one set with beef he raised the per- centage of females from 54 to 78 ; in the second lot, fed with fish, the jjercentage rose from 01 to 81; while in third lot, when the especially nutritious food of frogs was supplied, the per- centage rose from 50 to 92 ; thus in the last case the result of high feeding was that there were 92 females to 8 males. In the honey bee the queens are fed with richer, more nitrogenous food than the workers ; hence in the latter the ovaries are undeveloped; it is so with the white ants and ants. In the wasps when both males and females arise from fertilized eggs, Siebold's observations tend to show that predominance of females is due to better nutrition. Giron divided a flock of 300 ewes into equal parts, of which one-half were extremely well fed and served by two young rams, while those of the other half were served by two mature rams and kept pooidy fed. The pi-opor- tion of ewe lambs was 09 per cent, and 40 per cent. Busing's experiments leave little doubt that abundant moisture and food tend to produce females, while high temperature produces males; he found that the heavier, well-fed ewes produced ewes, while the lighter, under-fed ewes brought forth males. Sexual Diiiorphlsm. This is due to the rise of secondarj' characters. Such features are the male lion's mane, the horns of the buck, the gay plumage which distinguishes the cock from the hen, and the plumes, colored combs and wat- tles, top-knots, brilliant, conspicuous bands and spots, spurs, and those markings or new plum- age especially developed during the breeding sea- son. JIales tend among vertebrates to be larger, they lead the flock, guard the females and young; in character they are more jealous and pugna- cious. This is the case not only with mammals and birds, but with reptiles and frogs. The vociferous cries in spring of frogs and toads are mainly from male throats, the females being much less noisy. Certain fishes, as the salmon, during the breeding season are distinguished by bright colors and ornamental appendages. Of the invertebrates only insects, spiders, and Crustacea afford examples. Among coleoptera the stag- beetles (Lucanidte) are remarkable for their size and the enormous jaws and horns of the males, and there are two sets of males, those which in lack of armature approach the females, and those which are much larger and remarkably aberrant. In certain spiders the males arc gaily colored and their legs greatly modified in shape. Darwin has explained sexual dimorphism by his theory of sexual selection (q.v.). Sexual dimorphism reaches its acme in the males of certain solitary barnacles ; they are minute, very nuich reduced in structure, living inside the mantle-cavity of the female, where they are anchored by their antennae. In- Plants. The simplest plants give no indi- cation of any sexual process, but reproduce by cell division or by non-sexual spores. The gradual transition from the sexless to the sexual condi- tion is clearly shown in several groups of algse. For