116 Ilev. T. Hincks on Prof. Heller's Catalogue apex of the distal nectocalyx ; and liaving run along the poljpe-groove as far as the fundus of the nectosac, where it was surrounded by a tubular process of endoderm, it also ter-minated in a bifurcation, the resulting branches being distri-buted to the upper wall of the sac, as in the former case. Though the movements of Diphyes are very variable, the normal position is that in which the chaplet of polypes trails from the groove of the distal nectocalyx, the nectosac being-superior or on the neural side. The nectosacs give propulsion to the whole organism, with the pointed extremity of the proximal nectocalyx foremost ; nevertheless I am disposed to think that the movement is truly retrograde, as in the case of the cuttlefishes ; and if this be true, all the terms of relation used in the description of animals having a bilateral symmetry will be applicable to Dijihyes. H.M.S. 'Lord Warden.' Gibraltar, Oct. 10, 1871. XV. — Note on Prof. Heller's Catalogue of the Hydroida of the Adriatic'^. By the Eev. Thomas Hincks, B.A. We are indebted to Prof. Heller for very valuable contri-butions to our knowledge of the Invertebrate fauna of the Adriatic. In 1867 he published at Vienna an admirable Catalogue of the Polyzoa which occur in that sea, containing descriptions and figures of a large number of new s})ecies. In 1868 he continued his work, and dealt with the Zoophytes and Echinodermata of the same region, in the paper which is the subject of the present communication. The zoology of the Adriatic has been illustrated by a long line of able inves-tigators, extending from the times of Donati and Olivi (1750-1792) to the present day ; but Prof. Heller has shown us that its riches were far from being exhausted. It is unnecessary to say a word as to the value of such local catalogues and the relation which they bear to the interesting problems connected with geographical distribution. It is obvious, however, that, inasmuch as they form the storehouses from which the theorist draws his facts, it is of the first importance that they should be characterized by rigorous accuracy in the discrimination and identification of species. In that portion of his work which relates to the Hydi-oida, Prof. Heller has needlessly increased the chances of error, has rendered, indeed, a certain amount of * " Die Zoophyten uiid Ecliinodermen des Adriatischen Meeres, von Prof. Cam. Heller in Innsbruck," 18G8.
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