LEEUWENHOEK’S WRITINGS 391 
he assigned numbers—in chronological order. He published 
them, however, in two separate series—the first numbered 
with arabic numerals, the second with roman. But the first 
series began with No. 28* (not No. 1) and ran to No. 146, and 
thus consisted of 119 letters in all: while the later series 
(46 letters) was consistently numbered from I to XLVI. 
This, in itself, is apt to cause confusion: but the difficulty of 
collation is increased because the letters were not originally 
published always in strict chronological order, and were 
frequently, on their first issue, not numbered at all. Their 
seriation can therefore be determined only by their dates, or 
by the numbers assigned to them in later issues, editions, or 
translations. 
All the letters originally printed in Dutch, under Leeuwen- 
hoek’s supervision, were translated into Latin and printed in 
that language; but the Dutch and Latin versions were not 
issued simultaneously.” (As a rule—but not invariably—the 
Dutch versions preceded the Latin.) Furthermore, the letters 
—whether in Dutch or in Latin—generally made their appear- 
ance a few at a time in the form of a brochure with a common 
title: while a little later another collection would appear— 
often printed for a different publisher and with a different 
title—and in this some of the earlier letters were often incor- 
porated. The final complete collections of Leeuwenhoek’s 
letters were made up of these earlier partial collections—of 
various issues—and new editions; and, in the case of the 
Latin translations, sometimes of entirely new versions corrected. 
and amended almost beyond recognition. 
The following is a short list of the chief printed versions 
—both Dutch and Latin—which I have myself been able to 
study, together with a few notes [in square brackets] which 
may be serviceable to others. The arrangement is chrono- 
logical (for either language), and the names of publishers 
are given in parenthesis after the place and date of publica- 
tion. Numbers are prefixed merely for convenience of present 
reference, and have no other significance. 
1 Cf. p. 356 swpra, and Dobell (1931). 
2 By far the best list is that given in Harting (1876, pp. 132-139): but 
this publication is itself so rare that few authors can nowadays refer to it. 
My own copy was most generously presented to me by the late Prof. M. W. 
Beijerinck—after I had for years vainly attempted to obtain one through 
booksellers. 
