LETTER 18. CONCLUSION 163 
only that I haven’t descried them. And furthermore, I 
am persuaded that they would not be able to remain alive 
in the air, about our horizon; rather would they be 
begotten in the clouds, where, in the continual dampness, 
they could remain alive, and so be conveyed still living to 
us in mist and rain. I fancy I have even seen something 
of the sort in the early summer of this year, on two 
several occasions, when there was a heavy mist here; but 
I saw the supposed creatures without any motion. And 
I believe I have now found out a means of performing 
such observations more exactly and nicely in future. 
These observations concerning living creatures, in the 
liquors spoken of, were indeed deserving of closer atten- 
tion and description ; but for that, there had been need 
too of a whole man, which my circumstances did not allow 
of: for I have employed only my spare time upon them.’ 
Much light is thrown on the observations recorded in the 
foregoing letter by some of the Huygens correspondence. As 
the relevant MSS. are now accessible in print, and as it would 
take us too far afield to discuss the position of Huygens as 
a protozoologist, I shall not now consider this correspondence 
in detail. It is so important, however, that it cannot here be 
ignored, and I therefore add the following notes by way of 
supplement. 
Christiaan Huygens never himself published any serious 
contributions to protozoology: and the records of his own 
observations, which were made in an attempt to repeat 
Leeuwenhoek’s experiments, remained in manuscript and 
unknown until only a few years ago. Consequently, his 
private work” had no influence whatsoever upon the progress 
' A few final remarks—having no bearing upon animalcules—are here 
omitted. 
* Published for the first time in Gwvres Compl. de Chr. Huygens: see 
particularly Vol. VIII (1899), No. 2148, p. 122; and Vol. XIII, fase. ii 
(1916), p. 698 sq. So far as I am aware, all that was previously known 
about Huygens’s protozoological work is contained in the fragmentary notes 
in his Opuscula Posthuma (1703) and Opera Reliqua (1728). These show 
only that he was an imitator of L., and give no idea of the originality of 
his own observations. There is also a reference to the subject in Gregory 
(1713), however, while contemporary mention was made of his observations 
in the Journ. d. Scav. for 1678. 
