PROTOZOA OF FROGS DISCOVERED 233 
examined the said watery blood of divers frogs, that had 
run out into the dish (for I took a clean dish for each 
several frog), a very few animalcules were‘ to be seen in 
it once more. 
Because I couldn’t satisfy myself about the animalcules 
aforesaid, though I was sure they didn’t belong to the 
blood itself, but were gotten into it by accident; in the 
month of June* I continued my observations, and at 
last I came across some frogs* in whose dirt, which I 
took out of the guts, I beheld an unconceivably great 
company of living animalcules, and these of divers sorts 
and sizes. ‘The biggest sort “ had the shape of Fig. A.2 Of 
these I judged there were quite 40 in a quantity of 
material as big as a grain of sand. ‘The second sort” had 
the figure of B: these were very fewinnumber. The third 
sort had very near the shape of our river-eels, as Fig. C: 
these were in even greater plenty than the first. And 
moreover the whole material was so full of little animal- 
cules, that the very dirt seemed to consist of nothing but 
little living animals; for the little particles of the dirt 
itself were so stirred’ by the motions of the animalcules, 
that they looked almost as though they were themselves 
animalcules too.© The number of the little animalcules 
* is MS.—corrected to zijn in printed version. 
> Anno 1683. 
* The species is not discoverable from this description, but the protozoa 
found indicate that they were Rana esculenta—not R. temporaria. lL. knew 
well (and could distinguish) both species. In Letter 65, 7 Sept. 1688, he 
tells us that there are two kinds of frog (vorsch) in Holland—the common 
“kikvorsch”’ [= R. temporaria], and the larger “ work” [= R. esculenta] 
which is “ eaten by the French.” 
* Opalina (Cépédea) dimidiata—without a doubt. 
> hadden de fig: van. A MS. hadden de gedaante van Fig. 3. A. printed 
version. See Plate XXIII. 
° Nyctotherus cordiformis : but see below. 
"wiert . . . bewogen MS.—corrected to wierden . . . bewogenin 
print. 
* This graphic description must appeal to every worker who has studied 
the intestinal protozoa of frogs, for it vividly describes the usual appearance 
