270 
This widely distributed Cyclops appears but rarely in the records 
of the plankton of European lakes, and then only in the smaller 
ones. Stenroos (’98) reports it as abundant in the littoral zone of 
Nurmijarvi See; and Scourfield (798) finds it perennial and the 
most abundant species of Cyclops in the waters of Epping Forest. 
On the other hand it has been found generally in the plankton 
of European streams. Zimmer (99) finds it in the Oder, and 
Schorler (’00) states that it is abundant in April-June in the plank- 
ton of the Elbe at Dresden; Frié and Vavra (’01) find it only in the 
littoral fauna at Podiebrad; and Volk (’03) in the plankton in four 
of seven localities in the Elbe at Hamburg. Sowinski (’88) found 
it in the plankton of the Dnieper, Rossinski (’92) in that of the 
Moskwa, Zykoff (’00) in the summer plankton of the Volga, and 
Zernow (’01) in the winter plankton of the Schoschma. Meissner 
(702 and ’03) reports it in May—August as not abundant in the back- 
waters and vegetation of the Volga at Saratoff. 
In American waters Marsh (’93 and ’95) finds it in smaller lakes 
of Wisconsin and Michigan but not in the Great Lakes, and E. B. 
Forbes (’97) states that it is one of the most common and widely 
distributed species in American waters. It appears, however, not 
to be quantitatively an important element in lake or river plankton. 
Brewer (’98) finds it to be the most abundant vernal Cyclops in the 
small bodies of water near Lincoln, Neb. 
Cyclops viridis Jurine.—-A synonymy and a discussion of varia- 
tions in this the dominant and most variable of all the Cyclops in 
our channel plankton, has been given by E. B. Forbes (97). I have 
grouped the individuals in our plankton under two varieties, 
brevispinosus Herrick and insectus Forbes. The two varieties inter-_ 
grade, and in my separation I have followed only a single character 
readily visible without dissection or manipulation, namely, the 
outer terminal spine of the stylet, which is short, broad, and lance- 
shaped in brevispinosus, and more spine-like in imsectus. Judging 
from the results of this method of separation, it appears that this 
lance-shaped spine is a character of the male in many instances, 
though not found in all males or limited to this sex. 
Cyclops viridis var. brevispinosus Herrick.—Average number, 
124: in 1897, 447- in 1896,622- im 1895-8502 andim1894-63adehs 
form occurred in all months but January, but predominantly from 
the last days of April to the first week in October, the percentage 
