It lodges the copulatory organ, and on its dorsal wall lies the bursa Fabricii, an organ peculiar to birds.
Forbes, " On the Bursa Fabricii in Birds," P.Z.S., 18 77, pp. 304-318; H.
From this an equally slender tube proceeds, which joins its fellow of the opposite side, and the two form a thick, walled tube, which opens on to the exterior within the bursa copulatrix through which the penis protrudes.
In all these cases the female duct bears a bursa copulatrix or receptaculum seminis.
Many of the plants are annuals; among these are some of the commonest weeds of cultivation, shepherd's purse (Capsella Bursa-pastoris), charlock (Brassica Sinapis), and such common FIG.
C, Capsella Bursa-pastoris.
There is some reason to believe that this complicated and variable apparatus is used for stabbing the body of another animal and that beginning as a weapon for catching prey it has become modified for hypodermic impregnation and only gradually adapted for insertion into the bursa copulatrix.
From this junction there proceeds an oviduct or " uterus " (paired or single) which before opening to the exterior expands to form a muscular protrusible pouch - the bursa copulatrix.
Galle, Sp. agalla, a wind-gall or puffy distension of the synovial bursa on the fetlock joint of a horse, is derived from the Lat.