In _Ceratodus_ (Fig. 77), a long convoluted oviduct extends to the foremost limit of the abdominal cavity, where it opens by a slit at a considerable distance from the front end of the long ovary; this aperture is closed in sexually immature specimens. The oviducts unite close to their common opening in the cloaca. During their passage through the oviduct the ova receive a gelatinous covering secreted by its mucous membrane. This is probably also the case in _Lepidosiren_, which possesses a convoluted oviduct with secretory glands in the middle of its length. The oviduct begins with a funnel-shaped dilatation, and terminates in a wide pouch, which posteriorly communicates with that of the other side, both opening by a common aperture behind the urinary bladder. The ova of Ganoids, as far as they are known at present, are small, but enveloped in a gelatinous substance. In the Sturgeon have been counted as many as 7,635,200. Those of _Lepidosteus_ seem to be the largest, measuring 5 millimetres in diameter with their envelope, and 3 millimetres without it. They are deposited singly, like those of Newts. [Illustration: Fig. 77.--Ovaries of Ceratodus. _a_, Right ovary shown from the inner surface, which is covered by the peritoneum; _a’_, Left ovary, showing its outer surface; _l_, Portion of liver; _o_, Oviduct; _p_, the lower part of the oviduct is opened to show the folds of its inner membrane; _q_, Opening of the left oviduct into the right; _r_, Abdominal orifice of the oviduct.] In _Chondropterygians_ (and _Holocephali_) the organs of reproduction assume a more compact form, and are more free from a lengthened attachment to the back of the abdominal cavity. The ovaries of the majority are paired, single in the _Carchariidæ_ and _Scylliidæ_, one remaining undeveloped. But the oviducts are always paired, beginning immediately behind the diaphragma with a common aperture. They consist of two divisions, separated by a circular valve; the upper is narrow, and provided within its coats with a gland which secretes the leathery envelope in which most of the Chondropterygian ova are enclosed; the lower forms the uterine dilatation, in which the embryoes of the viviparous species are developed. Generally the vitelline sac of the embryoes is free, and without connection with the uterus, which in these cases has merely the function of a protecting pouch; but in Carcharias and Mustelus lævis a _placenta uterina_ is formed, the vascular walls of the vitelline sac forming plaits fitting into those of the membrane of the uterus. The ends of the uteri open by a common aperture behind the ureter into the cloaca. [Illustration: Fig. 78.--Ventral fins and claspers of Chiloscyllium trispeculare.]