Abstract: A fibrous plug to be inserted in a sucking tube for use for collecting and preserving sperma, fertilized ovum or the like in artificial fertilization or transplantation for human and animals, composed of a gelatinizing material component present in a gas-permeable dispersed form and a supporting fiber component, wherein the gelatinizing material component is distributed finely among the supporting fiber component, so as to permit swelling of the gelatinizing material upon contact with a water-containing substance, such as sperma or the like, to build up an intrgrated water-tight sealing stopper together with the supporting fiber component.