238 Miscellaneous, or two of this water and weed in his sitting-room for a few weeks. He will be rewarded by discovering rare forms of minute aquatic life. On examining a vessel of water brought from the canal, I discovered, in about a fortnight's time, the rare and beautiful Stephanoceros, several Melicertce, Paludicella and young Cristatellce. Paludicella, like Fredericella, is an exception to the rest of the family, being perennial. I remain. Gentlemen, Yours sincerely, W. Houghton. General Considei'ations on the Circulation of the lower Animals. By M. Lacaze-Duthiers. It is difficult to take up and irritate any mollusk, such as a snail or slug, but especially a marine mollusk, without observing that the animal, affected by the violent contractions caused in it by the in-stinct of self-preservation, allows to flow from its body a liquid often sufficiently abundant to moisten and bathe the hands of the observer. What is this liquid? whence does it come? how does it escape? It may be asserted that there exist a great number of animals of low organization, which, for purposes sometimes unkown, but often appreciable, deprive themselves, by bleeding, of a great part of the liquids of their economy. But it must be remarked that the same things do not take place in all groups, and that, to obtain an exact notion of the circulation in the lowest divisions of the animal kingdom, it is necessary to take our examples at once from the MoUusca, the Annulata, and the Zoophytes. In the first place, with regard to the MoUusca, positive facts now prove, beyond the least doubt, that there is a communication between their circulatory apparatus and the exterior world, MM. Langer and Gegenbaur have seen this in a Lamellibranch and in some Ptero-poda ; and I believe the former has demonstrated the existence of perfectly definite external orifices of the apparatus of circulation, serving for the issue of the blood or for the entrance of water, in the Gasteropoda, which are comparatively very high in the scale of MoUusca. The importance of such an arrangement will be understood with-out difficulty, and it will be seen how necessary it is to take it into account in studying the nutrition of these animals. We can hardly, therefore, bring too many jn'oofs in support of the demonstration of a fact so unprecedented and so little in accordance with what we observe in the higher animals. The new observations which I have the honour to present to the Academy are not isolated ; they are related to an ensemble of zoolo-gical researches upon the Gephyrea, Zoophytes, and MoUusca which I have pursued for a long time ; they were made at Cette in the months of August and September last. If the existence of external orifices of the apparatus of circulation in the MoUusca does not appear to be doubtful, it is nevertheless very difficult to ascertain. Thet]/s leporina of the Mediterranean,
BioStor
