LETTER 125. POLYSTOMELLA 263 
little cockles;* and these little shells were no bigger 
than a coarse sand-grain. 
In order to exhibit the pretty structure of these little 
shells before the eye, I thought ’twould not be amiss to 
set a drawing made of one of them. Fig. 7, ABC 
[Plate XX VII] shows one of these little cockles, which 
I took out of the stomach of a shrimp. 
It has been generally agreed that the shell here referred 
to was that of a Foraminiferan, but different writers have 
interpreted its species variously. For my part, I feel fairly 
confident that the picture represents a Polystomella.’ 
Leeuwenhoek’s next contribution to protozoology is 
imbedded in a _ well-known letter dealing chiefly with 
Rotifers: and the protozoological elements in this epistle 
have, it seems to me, been hitherto largely ignored or mis- 
understood. Too my mind there can be little doubt that he 
here left us an unambiguous record of his discovery of three 
different Protozoa—two Phytoflagellates (Haematococcus and 
Chlamydomonas) and a Ciliate (Coleps). But I will leave 
him to speak for himself: ° 
On the 25th of August,’ I saw that in a leaden gutter,’ 
on the front of my house, for a length of about five feet 
1 ven slakhoorntje. Hoole translates “snails”, but Sewel (1708) says 
the word denotes ‘a Cockle-shell’’; and from L.’s allusion to their 
roundness, I take this to be correct. The Latin translator called them 
limaces cochleares. 
2 Cole (1926, p. 13) takes the same view; but Miall (1912, p. 216) 
identifies the organism as Nonionina. Robert Hooke (1665, Obs. XI, p. 80; 
Scheme V, Fig. X) had previously described and figured a foraminiferan 
shell—probably Rotalia—which he had discovered in sand: but to L. his 
observation was apparently unknown. 
* Letter 144. 9 Feb. 1702. To Hendrik van Bleyswyk. Brieven (7de 
Vervolg), III, 400; Op. Omn. (Epist. Soc. Reg.), III, 380. No MS. and not 
in Phil. Trans. Partially translated into English by Hoole (1807), IJ, 
207.—Vandevelde says this letter is a “ Beschrijving van waterdiertjes, 
wellicht infusorién”’: but neither he nor anybody else appears to have 
sorted out the various “Infusoria’’ described, though Biitschli (Vol. II, 
p. 621) recognized Haematococcus. 
* Presumably anno 1701. 
> John Ray (in 1663) notes as a curiosity that in Holland “the Rain 
