178 LEEUWENHOEK AND HIS “LITTLE ANIMALS ”’ 
afterwards, to make his own remarkable contributions to 
protozoology.: 
It cannot be doubted that the “ very smallest animalcules,”’ 
of which Leeuwenhoek himself speaks, were in reality not 
protozoa but bacteria. The particulars which he records prove 
this conclusively, and it is hardly necessary to make infusions 
of pepper—as I have done*—to convince oneself of this: 
while the fact becomes superabundantly clear from Leeuwen- 
hoek’s next letter on this subject, which was written at the 
beginning of 1678 and contains the following remarkable 
passage *: 
I can't help mentioning that I can now make out, very 
plain and clear, the shape of those little animals of the 
smallest sort, whereof I said before* that I could ascribe 
no figure to them ; and this because of the pleasure that 
I do take in their manifold delightful structures, and the 
motions that they make from time to time in the water. 
Upon the 4th of this present month,’ when it froze hard, 
I did fill a small clean glass with pounded pepper to 3 of 
its height, adding § of rain-water, and set it for the first 
night in my bedchamber. The next day, it’ being well 
softened, I put it’ in my closet; and within thrice 24 
" See p. 163 supra. 
? Cf. also Beijerinck (1913). 
* From Letter 23,14 January 1678. This letter was written to Robert 
Hooke, who published an incomplete English version of it in his Lectures 
and Collections (1678), Part II; Letter 2, pp. 84-89. This translation was 
made by Hooke himself: for in a letter to L., dated 10 March 1682 (MS. 
unpublished), he says so, and adds: “I have as neere as I could followed 
the sense of your Expressions though not verbatim.’’—I translate from the 
original MS. I may add that this letter serves to confirm my numeration 
of L.’s early epistles: for it is No. 23 according to my reckoning, and L. 
himself refers to it in his 113th Letter as “my 23rd”. It was read at a 
meeting of the Society on 24 Jan. 1678 (cf. Birch, III, 380), but is not to be 
found in the Phil. Trans., nor in the Dutch or Latin editions of the letters. 
Hooke reprinted his translation in Lectiones Cutlerianae, Part V (1679). 
* Letter 18. (Seep. 143 supra.) The organisms referred to were evidently 
bacilli. 
° January, 1678. 
® ¢.e., the pepper. 
” i.e., the glass. 
