ANTHOPHYSA DISCUSSED 291 
is clotted together by some kind of mutual attraction. 
This won’t seem strange to us, if we bear in mind that 
whenever we file a bit of iron it gets rather hot; and if 
we apply the filed part to the filings, they’ll stay hanging 
chain-wise from it; though in nothing like the way 
such filings do with a lodestone. 
At this point Leeuwenhoek digresses into a description of 
some chemical experiments. ‘Then, after describing how he 
dissolved a little metallic silver in dilute nitric acid, he tells 
us how he witnessed the wonderful branching “ tree” which 
grew in this solution when he dropped into it “a particle of 
copper of the bigness of a sand-grain.” Such “trees” are 
now familiar to every schoolboy, but in Leeuwenhoek’s time 
they were novelties: nor has their wonder been wholly 
evaporated away by the work of modern chemists.’ It is 
clear, moreover, that Leeuwenhoek saw in the metallic “tree” 
a physical analogy—suggesting an explanation of its growth— 
to the ‘“‘tree” of Anthophysa, formed (in part) by the con- 
gealed particles of ferric hydroxide: for he adds ‘‘ I observed 
with a great deal of pleasure, how the Silver in this clear 
Water was coagulated into such bodies as are described by 
the above-mentioned Trees”’.*” Nevertheless, while recognizing 
the resemblances, he confesses that the process of growth is, 
in both cases, to him “ wholly inscrutable ”’. 
About 10 years later Leeuwenhoek sent another most 
interesting letter to the Royal Society—a letter in which he 
described anew his observations on Rotifers and Vorticellids. 
After referring to his previous observations on Melicerta, and 
its ciliary mechanism, he says :° 
1 Cf. Leduc (1911). 
® Chamberlayne’s translation.—L. gives a figure of his “ silver tree ”’ 
which is, I believe, the first ever published. His observations are, apparently, 
unknown to Leduc and other recent students of similar phenomena. 
° From Letter VII. 28 June 1713. To the Royal Society. MS.Roy.Soc. 
Published in Brieven, IV, 64 (1718); Epist. Physiol. (Op. Omn. IV), p. 63 
(1719). English translation printed in Phil. Trans. for 1713 [published 
1714], Vol. XXVIII, p.160. (The MS. of this translation—in an unknown 
hand—is preserved in the Roy. Soc. collection.) I translate directly from 
the original MS. in L.’s own hand. 
