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Show 1890.] ON ABNORMAL REPETITION OF PARTS IN ANIMALS. 579 ordinary prolongation of the azygos cardinal vein, though the vena cava was quite of the normal size. It will be observed that the continuity between the inter-renal portion of the vena cava and the azygos is quite in accord with the discoveries of Hochstetter1 in the development of these veins. Contrary to the generally received opinion (cf. for example the diagram illustrating the origin of these veins in Wiedersheim's ' Grun-driss der vergleichenden Anatomie der Wirbelthiere,' Jena, 1888, p. 329), Hochstetter found in the Rabbit and the Pig that the vena cava from where it receives the renal veins to a point behind the opening of the ilio-lumbar veins is formed from the right cardinal. 11. O n some Cases of Abnormal Repetition of Parts in Animals. By W I L L I A M B A T E S O N , M.A., Fellow of St. John's College, Cambridge, and Balfour Student in the University. [Received June 17, 1890.] This paper contains descriptions of some instances of variations consisting in abnormal repetitions of normal structures. A large number of similar or identical facts have already been recorded by many observers, yet every additional record is valuable ; for the significance of a variation depends not only on the form which it takes, but also on the frequency and the degree of completeness with which it takes that form. Though one is naturally tempted to draw seemingly obvious deductions from the facts about to be given, it is not proposed on the present occasion to do more than describe the actual structures as they are found. For while it is clear that the key to some of the problems of variation is to be sought by an analysis of this class of facts, yet such an analysis can only be attempted after a wide survey of the whole ground, and when it shall be possible to bring forward a large collection of the evidence bearing on the subject. I have been for some time engaged in preparing such a collection, and I hope before long to find an opportunity of putting it in order with a view to a full discussion of the modes of variation of Multiple Parts. In the meantime it is best to describe the forms without comment. I.- Crab (Cancer pagurus) having the Endopodite of the Third Maxillipede represented by a Chela. This animal was brought by a fisherman to the Laboratory of the Marine Biological Association at Plymouth. It is a male, measuring five inches from one side of the carapace to the other. All the 1 " Ueber die Bildung der hinteren Hohlvene bei den Satigethieren," Anz. Bd. ii. p. 517. |