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Wisconsin Academy of Sciences , Arts and Letters. 
cera. Doubtless more careful and prolonged collecting would disclose 
new species in both bodies of water, but the larger lake is certainly 
poorer in number of forms, especially the littoral species. The pelagic 
forms are, of course, more abundant in the larger lake, and one variety 
has been found in Lake Mendota which Lake Wingra does not possess. 
This single locality has yielded a number of species, comparing not 
unfavorably with the fauna described from England, Denmark or Russia. 
No European country shows more than 100 species; so that more than 
one-half of the probable fauna of Wisconsin has been found here. That 
so large a fraction of the entire fauna should belong to one locality will 
not appear strange when the similarity of the fauna to that of Europe is 
considered. If the species of Cladocera have so wide a range as appears 
from Sar’s observations on Australian Cladocera, and from my work 
here, it is not probable that many species are strictly local. We should 
expect to find any given species over a large extent of country in suita¬ 
ble localities. This expectation has been realized in many cases. As 
conspicuous instances I may note the occurrence of Drepanothrix 
dentata, Euren, in Wisconsin, the finding of Dunhevedict setiger , Birge, 
in Hungary by Daday, and the occurrence of Ilyocryptus longiremis, 
Sars, in Wisconsin and in Australia. No doubt some species are strictly 
local, confined to a small area, or the product of life-conditions existing 
there and not elsewhere. But the chance that this is true in any given 
case is small, and all well marked species should be looked for in every 
suitable locality. We should expect also that a locality especially favor¬ 
able to the development of the Cladocera would contain a very large 
fraction of the fauna of the region. 
The subjoined list also shows the value of long and careful collecting 
in one locality, and the impossibility of justly estimating the Cladocera 
of a lake from a single visit. The different forms behave much like the 
plants of a locality. Some species are present throughout the season. 
Some can be found only for a few days. Some come in the spring and 
disappear early, while others belong to the latter part of the open season. 
Of the nearly sixty species found in Lake Wingra I have never found 
more than thirty as the result of a single day’s work. It is clear that a 
list of Cladocera compiled from a flying visit to a locality and containing 
from six to twenty species, has no claim to represent the fauna of that 
locality. Only careful collecting at intervals throughout an entire sea¬ 
son can give even an approximate idea of the number of species 
present. 
I may add that a single specimen was found in Lake Wingra, belong¬ 
ing to the genus Anchistropus, Sars, and apparently not to the species 
emarginatus, Sars. It was accidentally destroyed before it could be 
carefully studied. 
