. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. [9-2] OVUM. of sexual union, and they are thence taken up singly by the open upper extremities of the two oviducts ; through the whole of which canals they descend, and in their passage receive an additional covering of a peculiar gelatinous or albuminous substance, which adheres closely to the surface of the yolk membrane, and is firm and of comparatively little bulk while the ova are still within the oviduct, but which after exclusion rapidly swells by the im- bibition of a large quantity of water, so as to become seve
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. [9-2] OVUM. of sexual union, and they are thence taken up singly by the open upper extremities of the two oviducts ; through the whole of which canals they descend, and in their passage receive an additional covering of a peculiar gelatinous or albuminous substance, which adheres closely to the surface of the yolk membrane, and is firm and of comparatively little bulk while the ova are still within the oviduct, but which after exclusion rapidly swells by the im- bibition of a large quantity of water, so as to become several times its original thickness, and to assume a soft gelatinous consistence. The ova which have passed through the oviducts remain for a time accumulated in large numbers in a dilated part of the canals near their lower end, until the whole or greater part of those which are ready to descend from the ovary have passed down ; and then, while the male still continues united with the female, the ova are rapidly excluded, and the male sheds the spermatic fluid in abundance, partly on the ova as they pass into the water, and partly alter separating from the female, upon the spawn as it floats in the water. The importance of the imbibition of water by the gelatinous covering immediately on the exclusion of the ova and just at the time when the spermatic fluid has been placed upon them, in securing the access of the sperma- tozoa to the surface of the vitelline membrane through the stiff jelly, and in thus promoting fecundation, will be afterwards more particu- larly adverted to. In the tailed Amphibia, such as the differ- ent kinds of Newt (Salamandra, Triton, and Lissotriton) there is not the same union of the male and female as in the tailless or Anu- rous Batrachia ; and impregnation takes place by the entrance of the spermatic fluid, shed in the water by the male while placed near the fe- male, into the oviducts of the hitter. In these animals the external covering consists of
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