A REVISION OF THE NORTH AMERICAN SPECIES 
OF CYCLOPS. 
C. DWIGHT MARSH. 
As collections are made more and more widely from all 
parts of the world and as these collections are studied more 
thoroughly, it becomes increasingly evident not only that the 
genus of Cyclops is distributed over the whole world, hut that 
individual species have an exceedingly wide distribution. 
Many of the species which have been described as peculiar to 
America have been clearly shown either to be identical with 
species in Europe or merely varieties of those species. Little 
by little it has been necessary to reduce to synonyms the 
names which have been proposed for American species. It 
can not yet be said that all American species are identical 
with those in Europe, but it is very evident that most of 
them are. Most of the species of Cyclops have wide limits of 
variation, and it is these variations which, at a time when the 
knowledge of the entomostraca was imperfect, lead to the intro¬ 
duction of many new names for species which we now know 
are only varieties. 
This leads to a great deal of confusion when students of 
anatomy or plankton, who may have no particular interest in 
a systematic knowledge of Entomostraca, attempt to name 
the species which they are studying. So great is this con¬ 
fusion that many students of plankton do not attempt to use 
specific names, but simply describe the distribution of 
“Cyclops/’ This is extremely unfortunate, for the species of 
Cyclops have very different habits and a discussion of plank- 
