252 
the few alcohol-preserved specimens and slides 
of dissected animals in the Marsh collections in 
the U. S. National Museum. Yeatman (1944) 
noted that the whole specimens were so thickly 
covered with ecto-commensal protozoans that 
details were difficult to observe. I also examined 
Marsh’s material and agree that it is difficult to 
study. Thus the availability of new specimens 
is of interest. Mrs. Mildred S. Wilson, Arctic 
Health Research Center, Anchorage, Alaska, 
forwarded some collections from Saint Matthew 
Island, Bering Strait. These collections were 
made by Dr. Robert Rausch and Reggie Rausch 
of the same Center. Dr. J. Kalff, Department of 
Zoology, McGill University, Montreal, sent 
several vials of Cyclops from the vicinity of 
Pt. Barrow, Alaska. 
comparison of C. kolensis with C. vie in us 
Four more or less consistent differences be- 
tween C. kolensis and C. vicinus appear to be 
in (1) the shape of the posterior corners of the 
4th thoracic segment, (2) the ratio of ramus 
length to width, (3) the ratio of inner terminal 
seta of ramus to outer terminal seta, and (4) the 
ratio of inner terminal seta to length of ramus. 
PACIFIC SCIENCE, Vol. XXII, April 1968 
Table 1 summarizes and compares these mor- 
phological features for the two species. 
The antennules of both C. vicinus and C. 
kolensis typically have 17 segments, although 
Kozminski (1934) noted that specimens with 
16 segments occasionally may be found. C. 
kolensis from Lake Baikal may have as many as 
18 segments in the antennule (Lindberg, 1955). 
C. vicinus and C. kolensis share the same spine 
formula on the outer margins of the terminal 
segments of the exopods of the swimming legs 
— 2, 3, 3, 3. A chitinous ridge occurs on the dorsal 
surface of each furcal ramus. 
Lilljeborg (1901) illustrated C. kolensis 
(Figs. 11 and 12) and C. vicinus (Figs. 16, 
17, 18, and 19). The 4th thoracic segment of 
C. kolensis is but little wider than the genital 
segment and is figured with blunt laterally 
directed projections. The rami are about 5 times 
as long as wide; the inner terminal setae are 
slightly longer than the rami ; the outer terminal 
setae are about two thirds the length of the 
inner. The seminal receptacle is shown as filling 
most of the genital segment. 
The 4th thoracic segment of C. vicinus is 
shown with sharply pointed wings which are 
laterally and posteriorly directed. It is much 
TABLE 1 
Morphological Characteristics of Cyclops kolensis and Cyclops vicinus 
as Described in the LiTERATURE a 
Cyclops kolensis 
Cyclops vicinus 
Posterior corners of the fourth thoracic segment 
rounded or produced laterally 
1, 6, 7, 11, 14, 15, 17 
Posterior corners of the fourth thoracic segment 
produced and expanded into posteriorly directed 
wings 
1 , 2, 3, 4, 8, 10, 11, 13, 15, 16 
Length of ramus 4 to 6 times the width 
1 , 4, 7, 11, 14, 15, 17 
Length of furcal ramus usually 7 to 8 times the width 
1 , 2, 3, 5 C , 7, 9, 10, 11, 13, 15 c , 16^ 
Inner terminal seta of ramus less than twice the 
length of the external terminal seta 
1 , 4, 11, 14, 15, 17 
Inner terminal seta of the ramus at least twice the 
length of the outer 
1 , 2, 3, 5, 7 e , 8, 9, 10, 11, 13, 15, 16 
Inner terminal seta of the ramus less than the length 
of the ramus 
1 , 4, 7 d , 11, 14, 17 
Inner terminal seta of the ramus exceeding or equal- 
ling the length of the ramus 
1 , 2, 3, 5, 10, 11, 13, 15, 16 
a The numbered references are: 1 , Borutsky I960; 2, Dussart 1958; 3, Gurney 1933; 4, Herbst 1955; 5, Kiefer 1937; 
6, Kozminski 1934; 7, Lindberg 1957; 8, Lint 1922; 9, Mann 1940; 10, Rylov 1935; 11, Rylov 1948; 12, Rzoska 1930; 13, Sars 
1918; 14, Kozhov 1963; 15, Lilljeborg 1901; 16, Uljanin, from Lint 1922; 17, Mazepova I960. 
b Seta equalling ramus. 
c 6 times. 
d Internal apical seta not as long as furca in C. kolensis alaskaensis\ internal apical seta exceeding ramus in C. kolensis 
kolensis. 
e Internal seta much less than twice the length of the outer in C. vicinus kikuch'r, internal 2 or more times the length of 
the external in C. vicinus vicinus. 
