OCR Text |
Show 1884.] ON AN ABDOMINAL VEIN IN ECHIDNA. 553 The facts contained in this paper appear to me to be an additional reason for uniting together the Storks and Herons more closely than was done by Garrod ; and the classification adopted by Mr. Sclater in the most recent edition of the ' List of Animals,' so far as this is concerned, expresses the facts. But it might be advisable to separate Scopus as the type of a family Scopidse, equivalent to both the Ardeidae and the Ciconiidae, and to place it between them as an indication that it forms a connecting link. It is not impossible that Balaniceps should also be included in this family. 4. Note on the Presence of an Anterior Abdominal Vein in Echidna. By F. E . B E D D A R D , M.A., F.B.S.E., Prosector to the Society. [Received November 11, 1884.] Although several excellent memoirs upon the various systems and organs of Echidna have from time to time appeared, there remain a considerable number of details of the structure of this most interesting mammal that require investigation. The death of the female specimen lately living in the Society's Menagerie has given me the opportunity not only of preserving certain parts for histological examination, but also of studying the anatomy of the animal in a fresh condition. In this way I have been able to make out a structural point which I believe has not been yet recorded, and which appears to m e to be of some interest-that is, the presence of an anterior abdominal or persistent allantoic vein. In the excellent account given by Prof. Balfour, in his ' Comparative Embryology,' of the development of the venous system in Verte-brata, I find the following statement;-" The venous system ' of mammals differs in two important points from that of Reptilia and Amphibia The anterior abdominal vein is only a fcetal vessel forming during foetal life, the allantoic vein." With regard to its subsequent history in Mammalia, Prof. Balfour says 2 : - " The allantoic (anterior abdominal) veins are originally paired. They are developed very early, and at first course along the still widely open somatic walls of the body, and fall into the single vitelline trunk in front. The right allantoic vein disappears before long, and the common trunk formed by the junction of the vitelline and allantoic veins becomes considerably elongated. This trunk is soon enveloped by the liver ... At the close of fcetal life the allantoic vein becomes obliterated up to its place of entrance into the liver . . . Owing to the allantoic (anterior abdominal) vein having merely a fcetal existence, an anastomosis between the iliac veins and the portal system by means of the anterior abdominal vein is not established." In the Reptilia and Amphibia, on the other hand, the anterior abdominal veins are represented in the adult condition as well as during fcetal life. In the Amphibia, as in the Mammalia, there are at first two abdo- 1 Comparative Embryology, vol. ii. p. 541. s Ibid. p. 546. |