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.
56/376 page 1456
![mutabile contain a parasite of the form of the yellow worms of Bojanus, which entirely fills their cavity. Is this the result of metamorphosis occurring during embryonic life? Other entozoa, namely, all the Nematoidea of Rudolphi, as the Ascaris, Strongylus, Oxyuris, Spiroptera, Trichocephalus, and Filaria, have the sexes on distinct individuals. Some worms also which do not belong to the class Entozoa, as, for example, the genus Gordeus, have the sexes distinct, and in that respect resemble the nematoid Entozoa. The Planariae, on the contrary, are hermaphrodite, as are likewise all the Annelida. Of the Mollusca, one entire order, the Cephalopoda, have the sexes distinct, while the Gasteropoda and Acephala have both hermaphrodite genera, and genera with distinct male and female individuals. The ma¬ jority of the genera of Gasteropoda are hermaphrodite; the Pectini- branchiata, however, as the Tritonium, Murex, Paludina, &c. have the sexes distinct.* The existence of the two sexes in the order Conchifera was known to Leeuwenhoek^ who recognised the ova and spermatozoa in distinct indi¬ viduals ; and this discovery, which was long neglected, has been recently confirmed in the most conclusive manner by Von Siebold. The ovaries or testes lie at each side of the foot, where this organ exists, and re¬ semble each other very closely in external characters; but are distin¬ guished by microscopic examination ; the ovaries of the female being found to contain merely ova with their essential parts, the germinal vesicle and germinal spot, and the testes of the male only spermatic animalcules. According to Siebold’s researches,']' the genera Anodonta, Unio, Mytilus, Tichogonia, Tellina, Cardium, and Mya, and, according to my own observation, Pholades also, have the sexes thus distinct. Some conchifera, however; have the sexes united ; for Wagner found both ova and spermatozoa in all the individuals of the genus Cyclas.^; Insecta, Arachnida, Crustacea, and all Vertebrata have the sexes dis¬ tinct; and the erroneous assertion that hermaphrodite genera, or genera having only the female sex, exist amongst them, has arisen from the superficial observation of the general similarity of form which the sexual organs sometimes present, for example, in many fishes; or from the com- * The Patella and Chiton also have been observed by R. Wagner (Froriep’s Not. xii. p. 7) to have distinct sexes. See also Edwards and Peters (L’Institut. 1840, No. 334), on the existence of distinct sexes in the genera Carinaria and Firola. Muller’s Arehiv. 1837, P- 381. $ See also Edwards on the hermaplirodism of the Pecten. L’Institut. 1840, p. 336. Krohn (Froriep’s Notiz. No. 356, 1842) says that the bivalve Clavagella is herma¬ phrodite. And Neuroylen states that the Rojanus's lung of the bivalves (Unio and Anodonta) is really a testis, and consequently that all these animals are herma¬ phrodite.](https://iiif.wellcomecollection.org/image/b29339601_0056.jp2/full/800%2C/0/default.jpg)
