Embryology, with the physiology of generation ... / Translated from the German, with notes, by William Baly ... From Müller's Elements of physiology and supplement.
- Johannes Peter Müller
- Date:
- 1848
Licence: Public Domain Mark
Credit: Embryology, with the physiology of generation ... / Translated from the German, with notes, by William Baly ... From Müller's Elements of physiology and supplement. Source: Wellcome Collection.
52/376 page 1452
![145:2 OF THE SEXES. organisation until they are acted on by another substance, allied to them, though distinct in its nature from them,—namely, the semen. The semen itself also propagates the peculiarities of the genus, species, and individual, but onty by means of its influence upon the ovum, which is the immediate seat of ail the changes attendant upon the production of a new individual. The semen and ova are sometimes generated in different individuals, in which case fecundation is effected by the concurrence of the two sexes, or by the contact of the semen of the one sex with the isolated ova of the other, brought together, artificially, out of the body. Some¬ times both semen and ova are formed in different organs of the same individual, which is the case in all hermaphrodite plants and animals. D ualism of the sex, therefore, does not necessarily involve dualism of the individuals ; on the contrary, sexual generation, as well as multipli¬ cation by buds and division, may be effected in a single individual. Animals having only the female sex were formerly supposed to exist; and, indeed, all the lower animals, for example, the polypes, Acalephae, and Echinodermata, were referred to that category ; ova being perceived in all the individuals of these orders of animals ; while the male organs, which are recognised less easily by the presence of spermatic animalcules, were not discovered. Since, however, double sexual organs are now known to exist in the Echinodermata, and since male organs have been demon¬ strated in the polypes, Medusae, Radiata, and Infusoria,* the notion that any animals are of the female sex alone is quite inadmissible. Besides, an ovum, capable of undergoing development without impregnation by male semen, would not be an ovum but a deciduous bud or gemmule ; and an animal producing such germs could not be regarded as of the female sex. There are many animals which form buds, but these buds are not deciduous ; they undergo development on the parent stock. Some animals, as Coenurus and Echinococcus, propagate by buds alone; others, on the contrary, as the polypes, both by buds and ova. In the Hydra, the ova as well as the buds appear on the surface of the cylindrical body in consequence of the ovaries having that situation ; but the ova are distinguished from the buds by their hard horny shell. In plants the male and female organs of generation are sometimes united in the same flowers ; sometimes developed in different flowers on the same stem (monoecious plants); and sometimes, lastly, wholly separated, different individuals of the species bearing either only male or only female organs (dioecious plants). The last mentioned arrange¬ ment of' the sexes is the most rare in plants, while in animals it is very * [The parts supposed by Ehrenbergh to be the sexual organs of the Infusoria are shown in figs. 14fi, and 147, page 14144.]](https://iiif.wellcomecollection.org/image/b29339601_0052.jp2/full/800%2C/0/default.jpg)
