MOLLUSCA. 
217 
Baltic itself^ but only in the brackish water near the mouths of 
the rivers. The breakwater leading to the lighthouse at Swine- 
miiiide, for instance, is occupied on the river side by Breissena, 
on the sea side by Mytilus edulis. 
Hr. Jackel, Hr. C. Stauue, and Dr. Fr. Buchenau have 
contributed further observations on this subject in the same 
journal, pp. 196, 228, and 278, in which they state that this 
slicll is found at present in the Wescr and in the Bavarian 
tributaries of the Main, even in the canal by which the 
Main has be^n connected with a confluent of the Danube ; so that 
Dreissena will shortly be an inhabitant of the upper and lower 
portions of the Danube without being found in the middle part of 
its course. 
Prof. E. A. Bossmassler, in his popular journal ^Aus der 
Heimath,' pp. 71-78 and 347-350, alludes to the same subject, 
principally its first appearance in Northern Germany, and states 
that the animal is able to detach the filaments by which it fixes 
itself to other objects, and that it is frequently found attached 
to the tail of crayfishes. 
Dr. Morch Pinna fluviatilis (Sander), Malak. Blatt. 
xii.pp. 110-117) defends his opinion (alluded to in the preceding 
note), viz. that a shell described by Sander in the year 1780 
from a rividet near Carlsruhe, is Dreissena, by an analysis of 
Sander’s account, and by the analogous fact that the occiurence 
of the genus Uiiio in Denmark remained unknown to so careful 
an observer as O. F. Muller (1773). But we cannot accept this 
as a very convincing argument, inasmuch as Unio has been in- 
cluded in all the faunas of the surrounding countries published 
at that time (of the Baltic provinces, Russia, North Germany, 
and England), whilst Dreissena is not mentioned in any of them. 
Hr. A. Gysser (Mai. Blatt. 1865, Literatur-blatt, p. 38) also - 
discusses this question. He lives at the place indicated by 
Sander, and expresses it as his opinion that the rivulet is a 
locality unfit for Dreissena, that Sander^s shell is a Unio hatavus, 
his description entirely agreeing with specimens from that loca- 
lity, with regard to size (two inches) as well as to coloration. 
A Dreissena of two inches would be a great rarity. 
Fischer, P. Acclimatation, en France, de Mollusques exo- 
tiques. Journ. Conch, xiii. pp. 65 & 66. 
Venus mereenaria and Ostrea virginiana, var. canadensis, have been brought 
alive to Bordeaux, and, having been placed in localities prepared for them 
in the years 1861 and 1863, the specimens have grown, but not propagated. 
Helix yucatanea, from the island of Carmen, Central America, has bred in 
France (Pep. Gironde), and the young ones were still alive at the beginning 
of the winter. Ibid. p. 69. 
