The _ova_ of Teleosteous Fishes are extremely variable in size, quite independently of the size of the parent species. The ova of large and small individuals of the same species, of course, do not differ in size; but, on the whole larger individuals produce a greater number of ova than smaller ones of the same species. The larger the size of the ova is in a species, the smaller is the number produced during one season. The ova of the Eel are almost microscopic. The small sized roe in the Herring, Lump-fish, Halibut, and Cod-fish, have been estimated at respectively 25,000, 155,000, 3,500,000, and 9,344,000. Larger in size and fewer in number are those of _Antennarius_, _Salmo_, _Aspredo_, _Lophobranchs_, etc. Comparatively largest are those of _Gastrosteus_; and the Siluroid genus _Arius_, the males of which take care of their progeny, produces ova from 5 to 10 millimeters in diameter. The ova of all Teleosteans are perfectly globular and soft-shelled. Teleosteans without oviduct, deposit them separated from one another; whilst in many Teleosteans with an oviduct the ova are enveloped in a glutinous substance, secreted by its glands, swelling in the water and forming lumps or cords, in which the ova are aggregated. [Illustration: Fig. 71. Ovum of Arius boakii (Ceylon), showing embryo. Nat. size.] [Illustration: Fig. 72.--Abdomen of _Aspredo batrachus_, with the ova attached; at _a_, the ova are removed, to show the spongy structure of the skin, and the processes filling the interspaces between the ova. (Natural size.)]