212 
The surprising fact derived from the examination of our records 
of this variety of C. viridis, is that the individuals referred to it are 
predominantly of the male sex. Out of a total of 74,308, 64,883, or 
88 per cent., are males, 8,542, or 11 per cent., females without eggs, 
and only 883, or one per cent., egg-bearing females. In so far as 
these data go, they indicate that this so-called species, or even 
variety, of C. viridis, in so far as it is based on the lance-like spine 
of the stylet, is not well founded. This is, it seems, predominantly 
a male character, though not exclusively so, since females, and even 
egg-bearing females, are found which exhibit this structure. 
C. viridis var. brevispinosus appears to be confined to American 
waters. Marsh (’93 and ’95) reports it from the larger lakes of 
Wisconsin and Michigan, and from the Great Lakes, except Lake 
Michigan. Birge (’95 and ’97) finds that it is the most abundant 
species of Cyclops (except in summer, when C. leuckartt abounds) 
in Lake Mendota, and the only one reproducing under the ice. His 
data exhibit a major pulse in May, and a second one, of less ampli- 
tude, in October, with slight indications of recurrent minor pulses 
in midsummer, obscured possibly by the massing of his data in 
fortnightly averages. The seasonal distribution in Lake Mendota 
is thus much lke that in the Illinois River. Marsh (’97) finds the 
maximum in Green Lake in June at 68°-69°, and only scattering 
occurrences at other seasons. E. B. Forbes finds this variety 
widely distributed in American waters, but never especially abun- 
dant. 
Cyclops viridis var. tnsectus Forbes.—Average number, 539; in 
1897, 2,115; in 1896, 949; in 1895, 2,966; and in 1894, 905. It is 
thus more abundant by two- to threefold in the stable years of 1895 
and 1897 than in the flood-swept years of 1896 and 1898. 
This variety was found in every month of the year, though 
predominantly in April-October, when the percentages of the 
collections containing it were respectively 64, 100, 85, 100, 100, 87, 
and 76 per cent. In November—March the percentages were only 
44, 6, 17, 7, and 13.. The numbers of individuals are very small, 
however, from October 1 to April 20, excepting in the autumn of 
1897, when, with the delayed high temperatures and the great 
impetus given to plankton development in the stable conditions of 
low water, the maximum pulse of all our records, 30,800 per m.*, was 
reached on October 5, a pulse of 1,200 following in November. With 
