LETTER 96. 9 NOVEMBER 1695 209 
In these my inquiries, I imagined that the unborn 
mussels got eaten up by the little animalcules aforesaid ; 
because it oft-times happened that I saw a multitude of 
little animalcules that had got between the shells of the 
young mussels, so that I judged, indeed, that I could even 
see as many as fifty animalcules inside a single young 
mussel. And during my observations, I observed that the 
fishy matter in the unborn mussels got less from day to 
day; nay, to such an extent even, that after the lapse of 
twelve days, little or no fishy matter was to be discerned 
between their little shells, which had become all trans- 
parent. After this time, too, I could not perceive that 
the animalcules were increasing in such great plenty. 
My notion that the little animals were partly the cause 
of the unborn mussels being eaten up (though ten 
thousand of the little animals aforesaid would, for the 
most part of them, scarce equal in bigness one of the little 
mussels), was confirmed when I came to inspect the little 
mussels (at the time when I had placed them in water in a 
white Delft porcelain basin) after inclosing them in various 
little glasses*; whereupon I perceived that each little 
mussel inclosed in the little glass, though also lying in 
water, still had its fishy substance between its shells, 
notwithstanding that many of them had their shells wide 
apart, or agape. 
I have sometimes been puzzled when beholding the 
multitude of little unborn mussels which lay inclosed in a 
big mussel ; for I was not able to conceive why our canals, 
and fens, are not overflowing with mussels, seeing that the 
water does not run so strong that it could carry the little 
mussels along with it, while they are still very small ; 
and in the second place, seeing that they are not gathered 
to serve as food: so that one mussel ought to beget 
thousands. But now, after discovering how the little 
" As mentioned below, these “little glasses” (glaasjens) were capillary 
glass tubes, such as L. commonly employed in his experiments. 
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