167 
CHAPTER 2 
EPILOGUE TO LETTER 18. FURTHER OBSERVA- 
TIONS ON THE FREE-LIVING PROTOZOA AND 
BACTERIA 
(LETTERS 19, 21, 23, 26, 29a, 30, 31, 32, 33, 71, 92, 96) 
S we have already seen, Leeuwenhoek communicated his 
A discovery of the Protozoa and Bacteria not only to the 
Royal Society but also to Sir Constantijn Huygens. 
The latter evidently wrote a reply—which is lost—to which 
Leeuwenhoek rejoined, inter alia’: 
In order to answer Your Excellency’s letter further, I 
must yet wait 2 or 3 weeks, for the reason that I have to 
repeat the observations I made some time since (concern- 
ing the living creatures in water) with two kinds of 
water, which, among others, I intend to study every day. 
From these words it may be inferred that at the beginning 
of 1677 Leeuwenhoek was still hard at work on his discoveries. 
But the Royal Society also did not remain idle or disinterested : 
the Fellows wanted to know more. Consequently, in an 
editorial comment upon Leeuwenhoek’s observations on the 
animalcules in pepper-water “—wherein he says that he saw 
‘ several thousands of the very small animalcules”’ in a single 
drop of liquid—Oldenburg remarks*: “ This Phaenomenon, 
and some of the following ones seeming to be very extraordinary, 
the Author hath been desired to acquaint us with his method of 
observing, that others may confirm such Observations as these.” 
"From Letter dated 15 February 1677. To Const. Huygens sen. The 
original Dutch MS. is at Leyden, and has recently been printed in Zwvr. 
Compl. de Chr. Huygens (1899), Vol. VIII, No. 2099, p. 21. 
* See p. 135 supra, 2nd observation on pepper-water: 24 May 1676. 
® Phil. Trans. (1677), Vol. XII, p. 829. 
