The preceding objects are represented of their natural size, and as they lost their colour during the first maceration in water, owing to the great readiness with which the mossy vessels discharge their blood, the colour adopted in the Plate is that which they attain afterwards, and such as it appeared when the artist sketched them. They have in every instance been examined and dissected under water. Such early Ovula are not rare. In the Museum of the Royal College of Surgeons of London there are four such specimens, marked 3432—3—4—5 in red ink on the black varnished cover of the bottles[26]. In Sir Charles Clarke’s collection there are also several. I have likewise examined many of them in Meckel’s magnificent museum; but it is in that of the late Professor Sœmmering that I have been gratified by the sight of not a few beautifully prepared and arranged specimens of this early stage of the human Ovum. Among them were the identical preparations which he selected and arranged in a graduated series of human embryos, and afterwards caused to be delineated and engraved, for his valuable work entitled “_Icones Embryonum humanorum_.” Fig. 5. The rudiments of the embryo in this specimen are more than usually diminutive, compared to the mass which constituted the entire Ovum before it was flattened and pinned to a piece of blue pasteboard placed in spirits within a glass jar. This preparation, now in the museum of St. George’s Hospital, exhibits the transparent involucra and the placental envelope with the intermediate membranes, imperfectly developed, of an Ovum which I should judge to have been fecundated about three weeks. At this period of conception the embryo is generally straight, consisting of that part which is to be the trunk, terminated, as in this case, by a round swelling, which is the head. Here the embryo is in reality straight, and has the appearance of a worm. It is attached to the inside of the secreting membrane by its abdominal surface without any visible cord. As illustrative, and that in a very distinct manner, of this early stage of pregnancy, Fig. 5 is a valuable specimen. Fig. 6. The same remarks apply to this as to No. 5. The embryo is somewhat more clearly delineated. Its trunk is gently curved forward, and the tubercular-like rudiments of the extremities appear visibly marked. This circumstance denotes its age to be of five weeks.