67 
On Naked Fresh-Water Radiolaria. By Dr. Gustav 
Woldemer Focke, of Bremen . 1 
The distribution of animals in the older strata of the earth’s 
crust would lead one to assume that fresh-water lakes could not 
have been inhabited until a late period, and, indeed, the distri- 
bution of living beings in fresh and salt waters is now very dis- 
proportionate. With regard to many orders of the animal 
kingdom, nature seems to have made some feeble attempts to 
populate fresh waters, and then to have given up the matter ; 
with others the distribution in both quarters is tolerably equal, 
although no very important physiological differences seem to 
exist; with the majority the sea presents a most decided pre- 
dominance. Until recently Radiolaria have been found only 
in the sea, or at least shell-less free-living forms have never 
yet been observed in fresh water. In the middle of last 
summer I, to my great surprise, discovered at the same 
source three different kinds of creatures which presented 
decided characters of Radiolaria. As most of the inhabitants 
of the sea belonging to this order are enclosed in hard 
porous shells, the examination of their tissue elements is 
rendered difficult to a great degree ; consequently, the oppor- 
tunity of examining these free-living forms from fresh water 
offer a very desirable facility for making a minute investigation. 
Unfortunately the information which can be supplied con- 
cerning these creatures is as yet extremely fragmentary. Of 
the history of their development no particulars can be given. 
The present report, therefore, will merely indicate the exist- 
ence of shell-less fresh-water Radiolaria, in order to give some 
notion of the facts relating to them, and to attract the atten- 
tion of any other observer, since the systematic determina- 
tion and the physiological description of these creatures can- 
not be attempted with any prospect of success until more 
minute investigations have been made. The creatures have 
a restricted range of locality, and in that range are probably 
quite as scarce, since numerous organisms, some of which are 
smaller, existing together with them, have been recognised 
for a long time, and minutely described. The locality in 
which fresh-water Radiolaria have been found is moor-pools, 
that is to say, places in peat moors into which flow streams 
from neighbouring sandy parts or old waste downs; into 
these is discharged a scanty stream of water, which remains 
1 Dr. Focke is evidently unaware of the researches of Mr. Archer, of 
Dublin, on this subject, who has already in this Journal characterised one, at 
least, of Dr. Focke’s genera. See “ Dublin Club Minutes.” 
