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 
Melicerte, Paludicella and young Cristatelle. Paludicella, like 
Fredericella, is an exception to the rest of the family, being perennial. 
I remain, Gentlemen, 
Yours sincerely, 
W. Hoveuron. 
General Considerations on the Circulation of the lower Animals. 
By M. Lacaze-DuruieErs. 
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 im- 
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 Mollusca, the 
Annulata, and the Zoophytes. 
In the first place, with regard to the Mollusca, 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 
Mollusca. 
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, brmg too many proofs 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 Mollusca 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 Mollusca does not appear to be doubtful, it is nevertheless 
very difficult to ascertain. Thetys leporina of the Mediterranean, 
