394 SUPPLEMENT 
quire of being poisonous, when they have eaten that of the 
asteriz. 
It is certain that the mussels are hermaphrodites, like the 
others of the same tribe; that is, all the individuals are 
similar, or a single one constitutes the species. 
The female product of generation does not come from the 
mother in a perfect state. It is rejected in the form of a 
gelatinous substance, in which are contained the germs of the 
young mussels. The latter, no larger as yet than a grain of 
millet, already have their byssus, which, most likely, is born 
with them, and which, probably, serves to attach them, with 
the assistance of the linguiform appendage of the mother. 
The species of this genus live in assemblages, more or less 
numerous, usually placed in a compact manner, one against 
the other, fixed more or less solidly by their byssus, in an 
oblique situation, the top of the shell being undermost and 
behind ; the base, or broadest part of the shell, is uppermost, 
the two valves being a little open. ‘Through this semi-aper- 
ture, the fringe which edges the mantle comes out behind, 
and the filaments of the byssus pass through the emargination 
of the ventral edge. 
Some species are thus placed at the superficies of bodies ; 
others, in preference, seek the excavations which may exist 
in such bodies. Finally, some species excavate a lodge for 
themselves, like the other lithophagous bivalves. It also ap- 
pears that some live sunk in mud, like the pinne. It is pro- 
bable that they have a thicker byssus, contrary to the litho- 
domous species, in which it is very small, and even does not 
exist except in youth. As their shell closes exactly, they can 
very well support the alternation of the flux and reflux upon 
our coasts, and thus live during six hours out of the water, 
but in general they are more constantly submerged. 
Mussels are almost always found in salt, or at least in 
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