396 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”’ 
29. OPERA OMNIA, seu Arcana Naturae, ope Exactissimorum Microscopiorum 
Detecta, experimentis variis comprobata, Epistolis, ad varios illustres 
Viros, ut et ad integram, quae Londini floret, sapientem Societatem 
... datis. 4°. 4Avols. Lugduni Batavorum, 1722 (Langerak).— 
This is the Latin equivalent of No. 20, and contains all the Epistolae 
from 28 to 146 and I-XLVI. It is made up of various editions and 
issues, and most copies which I have collated are imperfect. The 
usual arrangement is as follows (though many other collections 
are to be found) : 
Vol. I = Nos. 23a (part i), 22 (ii), 240. [Engraved title of No. 25, 
general title, and 12 other preliminary pages (carmen panegyricum, 
lectort typographus, & index): pp. 1-64 + 1-260: Index triplex 
[pp. xxiv]: title, pp. vi (fraemonitio ad lectorem & index) + 
1-124. Contains, therefore, Letters 43, 42, 38; 28, 29, 30, 31, 
34, 35, 36, 46, 47, 44, 45, 48, 49, 50, 51, 52; 53-60.] 
Vol. II = Nos. 25¢ & 26a. [Engraved title of Nos. 8 & 22, 
with new Latin lettering; new titlepage + pp. xiv (index) 
+ 1-515; Index (pp. xxiii + errata) ; new titlepage + Index 
argumentorum (pp. vill) + pp. 1-192 + Index (pp. viii). Contains, 
therefore, Letters 32, 33, 37, 39, 40, 41, 61-92 ; and 93-107.] 
Vol. III = No. 27. [Portrait + title with engraved device 
+ pp. xiv (index 1) + pp. 1-429 + x (index 2). Containing 
Letters 108-146. ] 
Vol. IV = No. 28. [Containing Letters I-XLVI.] 
* All these volumes contain numerous figures engraved in the text 
and on large and small inserted plates—identical with those 
of No. 20. 
In addition to the foregoing publications, I must record the following— 
issued in Leeuwenhoek’s lifetime but not by himself. [All the 
original MSS. appear to be lost.] 
The Letters addressed to Petrus Rabus.—Pieter Rabus (1660-1702 ; 
Dutch author, poet, and critic) published in the last decade of 
the XVII Century a literary review entitled ‘“‘ De Boekzaal van 
Europe”’ (8°. Rotterdam). Two volumes were issued yearly— 
separately paged—from 1693 to 1700: and in those published 
between 1693 and 1697 Rabus not only reviewed those works 
of Leeuwenhoek which appeared contemporaneously, but he 
also printed several of his letters addressed to himself. As 
these are not to be found elsewhere, and as they are not correctly 
cited by van der Aa or others, I add exact references here. Apart 
from reviews, and letters printed elsewhere, Rabus published— 
more or less completely—six of L.’s letters which are otherwise 
unknown. To wit: . 
1. A letter dated 27 Oct. 1693. Boekzaal v. Europe 16938 (ii), 
pp. 554-5. [Extract only.] 
2. Letter dated 21 May 1695. Jbzd., 1695 (i), pp. 532-6. 
{Extract.] 
3. Letter undated. Jbid., 1695 (ii), pp. 96-9. 
