424 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS” 
Professor M. W. Beijerinck of Delft, with characteristic 
unselfishness gave me aid both material and spiritual. The 
late Mr L. G. N. Bouricius, Archivist of Delft until his 
untimely death on 21 February 1929, also supphed me with 
much valuable information, and never failed to satisfy my 
frequent inquiries to the utmost of his ability. Dr W.H. van 
Seters of Leyden, who recently produced the ‘“ Leeuwenhoek 
Film,” most kindly communicated—unasked—all his own 
incidental findings, together with several original photographs 
and a full copy of the captions. Dr E. P. Snijders—formerly 
stationed in Sumatra, now Professor at Amsterdam—has given 
me not only valuable advice but also a magnificent specimen 
of the old Dutch Bible (1702): while Dr A. Schierbeek, at 
The Hague, has rendered the kindest assistance in innumerable 
ways during the last ten years. To all these unseen Dutch 
friends and fellow-students of Leeuwenhoek I owe a debt 
which I can never acknowledge sufficiently. They have all 
given mé—a foreigner unknown to them _ personally—their 
most generous help. Dr C. A. Crommelin, now Professor 
of Physics at Leyden, has been equally helpful: but I 
mention him separately because he is, happily, not only still 
a living student and admirer of Leeuwenhoek but also one 
whose hand I have actually shaken. I would also record that 
the Netherlands Society of Sciences, at Haarlem, have aided 
me by the gift of two important volumes of the Complete 
Works of Huygens, which they are editing and publishing on 
so sumptuous a scale. 
Among my own countrymen who have given me continued 
support I must mention particularly Professor William 
Bulloch, F.R.S., and Professor F. J. Cole, F.R.S. The first— 
as all real students everywhere know— possesses an unrivalled 
knowledge of the history of bacteriology (and of medicine in 
general): the second is now our only living authority on the 
history of zoology. Both have given me the benefit of their 
own solid learning on countless occasions. If I have not 
profited by it, the fault is mine. 
To the Council of the Royal Society I am beholden for 
sranting me the facilities necessary to undertake this work ; 
and to the Trustees of the National Gallery and the Directors 
of the Rijks-Museum and the Mauritshuis for permission to 
reproduce the pictures shown in four of my plates. 
Finally, I wish to acknowledge my deep personal obligation 
