LETTER 144. 9 FEBRUARY 1702 265 
The smallest animalcules of this sort I judged to have 
been begotten of the bigger ones. 
I did also see yet another kind of animalcules, that 
were much smaller.’ These were very clear in the body ; 
but I judged that there must have been quite a hundred 
of the former sort to every one of the latter. 
On the 31st of August, the water was so far dried up 
(owing to the great heat, which had continued for three 
days running), that if I pressed my finger on the dirt” 
lying on the lead, little more than a drop of water as big 
as a sandgrain stuck to it: and though I could discern a 
few living animalcules, which were transparent, in this 
water, yet all the green and red ones were dead. 
On the Ist of September, the stuff in the leaden gutter 
was become so thick, that it was like stiff wet clay; and 
notwithstanding all my efforts, I could discover no living 
creatures in it of the sort that I had seen before. 
At this point Leeuwenhoek leaves Haematococcus and goes 
on to describe the Rotifers which he also discovered in his 
leaden gutter; but in the course of his description he 
accurately notes that: 
The stuff in the guts of these little animals ° was most 
always red, proceeding (as I imagined) from the red 
animalcules* which they use as food: but I also saw 
afterwards a few of these little animals which hadn’t 
any of the red stuff inside them, particularly the young 
ones which had not long left their mother’s body. 
Here follow further observations on Rotifers—including 
the famous experiment in which Leeuwenhoek found that 
1 Possibly bacteria, but obviously unidentifiable from this slight 
description. 
2 A little later (4 Nov. 1704) L. says—in the words of a contemporary 
English translator (MS.Roy.Soc.)—* I don’t suffer such foul stuf to lye long 
in my gutter, but twice a year cause the lead to be scowered so clean that 
it looks just like new’”’. 
* t.e., Rotifers. 
4: 
2.€., Haematococcus. 
