CILIARY MECHANISMS 295 
Can anybody doubt, after reading the foregoing words, 
that Leeuwenhoek had, in 1718, already discovered the chief 
function of the peristomial cilia (“ wheelwork”’) of Vorticella ? 
Surely not. Old Antony knew as well as I do (and everybody 
else now does) how the Vorticellids, and many other ciliated 
organisms, capture their food from the surrounding water— 
though he misconceived the structure of the mechanism. By 
persistent study he had advanced a long way beyond his 
original interpretations of 1676,‘ and had at last reached the 
truth. 
The remainder of this letter contains some further observa- 
tions on “‘animalcules”’: and as some of these—though none 
is exactly identifiable—were undoubtedly protozoa and 
bacteria, I will now quote what else he here relates : ° 
At the beginning of the month of August,’ I was in a 
garden where there was a pond well stocked with fish ; 
and pretty well all over the water there floated a thin 
scum, which looked greenish, though you couldn’t see any 
other green-stuff in the water: which seemed to me odd, 
because in other years* I had noticed that the water was 
very clear in this pond, as it was also in the ditch from 
which the pond was continually replenished; but I was 
told that when it rains, the scum goes away. 
I went a little aside, all on my own, and took a wooden 
lath, with which I touched the surface of the water ; and 
putting a little drop of the water in a green wine-glass, I 
looked at it through a microscope that I had by me: and 
I discovered in this water so unbelievably many little 
animalcules, which even through a microscope are scarce 
discernible, that no one could be made to credit it, unless 
he got a sight of it for himself; and also divers sorts of 
1 Cf. p. 118 supra. 
2 The passages which follow begin at the top of p. 68 of the Dutch 
printed works (Vol. IV, Send-brieven). 
* Presumably anno 1712: but from the final paragraph this is not 
certain. 
* op andere jaren MS. “at other times”? Phil. Trans. 
