The Crayfish: An Introduction to the Study of Zoology.

by Thomas Henry Huxley

These two kinds of living matter are ova and spermatozoa, and they are developed in special organs, the ovary and the testis. The ovary is lodged in the female; the testis, in the male.

The ovary (fig. [30], ov) is a body of a trefoil form, which is situated immediately beneath, or in front of, the heart, between the floor of the pericardial sinus and the alimentary canal. From the ventral face of this organ two short and wide canals, the oviducts (od), lead down to the bases of the second pair of walking limbs, and terminate in the apertures (od′) already noticed there.

FIG. 30.—Astacus fluviatilis.—The female reproductive organs (× 2); ov, ovary; od, oviduct; od′, aperture of oviduct.

FIG. 31.—Astacus fluviatilis.—The male reproductive organs (× 2); t, testis; vd, vas deferens; vd′, aperture of vas deferens.

The testis (fig. [31], t) is somewhat similar in form to the ovary, but, the three divisions are much narrower {130} and more elongated: the hinder median division lies under the heart; the anterior divisions are situated between the heart behind, and the stomach and the liver in front (figs. [5] and [12], t). From the point at which the three divisions join, proceed two ducts, which are termed the vasa deferentia (fig. [31], vd). These are very narrow, long, and make many coils before they reach the apertures upon the bases of the hindermost pair of walking limbs, by which they open externally (fig. [31], vd′, and fig. [35], vd). Both the ovary and the testis are very much larger {131} during the breeding season than at other times; the large brownish-yellow eggs become conspicuous in the ovary, and the testis assumes a milk-white colour, at this period.

FIG. 32.—Astacus fluviatilis.—A, a two-thirds grown egg contained in its ovisac (× 50); B, an egg removed from the ovisac (× 10); C, a portion of the wall of an ovisac with the adjacent portion of the contained egg, highly magnified; ep, epithelium of ovisac; gs, germinal spots; gv, germinal vesicle; m, membrana propria; v, vitellus; vm, vitelline membrane; w, stalk of ovisac.