116 LEEUWENHOEK AND HIS “LITTLE ANIMALS” 
the extensive investigations described in the original Dutch 
epistle (Letter 18). 
The greater part of this very long letter—one of the 
longest Leeuwenhoek ever wrote—is in an unusual form. At 
the very end of it he remarks that “these my observations” 
are “ taken from the diary which I keep from time to time;” 
and accordingly we find that he generally gives, in order, the 
observations as he made them from day to day—without 
making any attempt to summarize or correlate them. In his 
letter to Constantijn Huygens (7 Nov. 1676) he explains that 
he sent these details from his notebook “ merely so as to make 
my observations more credible in England and elsewhere; and 
especially because Mr Secretary Oldenburg had formerly 
written to me that there are a number of philosophers at Paris 
and elsewhere who don’t allow of the truth of what I 
describe”*. The subject-matter falls naturally, as will be 
seen, into various sections, dealing with the divers creatures 
found in the several sorts of water or infusions which he 
examined. Some of these sections are provided, by himself, 
with appropriate headings, while others are not: and I have 
therefore, for the sake of uniformity, interpolated such 
headings where they are lacking in the original.’ 
Leeuwenhoek’s 18th Letter opens (cf. Plate XIX) with a 
few personal remarks, of no particular interest in the present 
connexion, and then drops abruptly into the description of his 
discoveries: and at this point I have begun my translation, 
which now follows.* 
* Another French translation (or a copy of one of the two mentioned 
above ?) was published later in a work called Collection Académique de Dijon, 
Vol. II, pp. 454-461, 1755: but this I have not been able to consult. Cf. 
Konarski (1895, p. 251 note) and Vandevelde (1922, p.349)—No account of 
these observations appears to have been published in the Acta Hruditorum, 
which only began publication in 1682: but a reference to L., and the 
discovery of animalcules in infusions (attributed ambiguously to Butterfield), 
will be found in the note by Elsholz (1679) in Miscellanea Curiosa, Vol. IX. 
* See Vandevelde and van Seters (1925), p.20: and Guvres Compl. de 
Chr. Huygens (1899), Vol. VIII, p. 22, footnote 3. 
* These additions, wherever they occur, are indicated by being inclosed 
between square brackets. 
* Letter 18. 9 October 1676. To Oldenburg. MS. Roy. Soc. I have 
not thought it necessary to mark all the places where my translation differs 
