Archive image from page 69 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana05todd Year: 1859 50 OVUM. the eel among the osseous fishes, the oviduct is entirely wanting, and the numerous ova which are dischargee by external dehiscence from the ovary into the cavity of the abdomen, escape from that cavity by an orifice (porus abdominalis) situated on each side close to the anus. 4th. In other osseous fishes, the ovary and oviduct are united, or the ovary forms a saccular organ, in the interior of the wall of which the ovi- capsules are situated, occupyin
Archive image from page 69 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana05todd Year: 1859 50 OVUM. the eel among the osseous fishes, the oviduct is entirely wanting, and the numerous ova which are dischargee by external dehiscence from the ovary into the cavity of the abdomen, escape from that cavity by an orifice (porus abdominalis) situated on each side close to the anus. 4th. In other osseous fishes, the ovary and oviduct are united, or the ovary forms a saccular organ, in the interior of the wall of which the ovi- capsules are situated, occupying a variable extent of it in different genera ; and the wall of the oviduct, usually very short, is continued from that of the ovary to the outlet from the animal's body. The ova, therefore, which drop by internal dehiscence into the cavity of the ovary, pass directly out by the short ovi- duct in the laying of the spawn. Most osseous fishes are oviparous; but in a few, as the viviparous blenny, the anableps, paecilia, and some siluroids, the ova, on escaping from their capsules into the cavity of the ovary, remain there during the development of the embryo. In the invertebrate animals there are very many varieties in the form and relations of the productive and conducting parts of the organs. Three principal female generative Fig. 40. Oviduct and ovary in a continuous tube in Insects and Entozod. A. (From R. Wagner}. Upper part of the ovi- duct or ovary of the Acheta campestris. B. (From H. Nelson.} Upper part of the oviduct or ovary of the Ascaris mystax. In both of these figures the germ-cells and germinal vesicles, with their nuclei, are seen surrounded by the granular matter which afterwards collects round them as vitelline or yolk substance. varieties may be distinguished among them 1 st. A form similar to that just now described as generally prevalent among osseous fishes, in which the ovary and oviduct are con- tinuous, but in which the ova, being formed in ovarian
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