Marsh—North American Species of Cyclops. 1077 
The work of Miss Lehmann (Lehmann J 03) proved this in 
regard to the distinctions between brevispinosus and amerir 
canus. And jet I am inclined to put much more stress than 
does Forbes on the varietal distinctions. While we can find 
connecting forms, if we look for them, jet it is true that col¬ 
lections from anj locality are apt to contain onlj one varietj 
in abundance. It is true that one can find the blunt furcal 
spine of brevispinosus merging bj insensible stages into a 
seta, but it is also true that we can make collections in which 
practicallj all the individuals have the blunt spine. These 
same individuals will have, correlated with the blunt spine, 
elongated furcal rami, a formula for the spines of the terminal 
segments of the exopodites of the swimming feet represented 
bj 3, 4, 4, 4, and a spine on the external margin of the 
terminal segment of the endopodite of the fourth swimming 
feet. One maj find brevispinosus forms with a seta on the ex¬ 
ternal margin of the terminal segment of the endopodite of the 
fourth swimming foot, hut this is hj no means common. So 
when one finds parcus forms he is not likelj to find other forms 
mingled with it. So with the americanus. There are grades 
connecting this with the other varieties, hut in anj given col¬ 
lection where americanus is found, nearlj all will be tjpical 
americanus. 
It is true that the armature of the swimming feet maj 
varj, hut variation is not so common, in mj experience, as 
would be inferred from the statements of Forbes. I have even 
found a form in which the right and left fourth feet in the 
same individual had a different spinous armature, but this is 
so unusual, that it maj he considered, in all probability, as 
the result of some mutilation. 
I have sometimes thought that we might well consider these 
varieties as distinct species, and that the intermediate forms 
were the result of hjbridizing. Whether this is true or not 
could onlj he determined bj a course of breeding, and it is 
likelj to be a long time before we shall know the pedigrees of 
the species of Cyclops. Meantime students who must discuss 
these forms as elements in the plankton, and who, perhaps, 
have no interest in the taxonomic side of the question, must 
