Marsh—North American Species of Cyclops . 1081 
although it is not confined to them. I have already discussed 
(Marsh 1903) its occurrence in Wisconsin lakes. It seems to 
prefer cold water, and my work in Wisconsin seemed to show 
that it might be considered as preeminently a winter form. 
Miss Pratt (Pratt 1898) finds it a winter form in Lake 
Bassenthwaite in England. I have found it in small bodies 
of water in Indiana in the winter, while in the cold lakes of 
the Pocky Mountains it is a summer form. 
Birge and Juday, in a recent paper (Birge and Juday 
1908) have noted an interesting fact in the life history of C* 
bicuspidatus. In certain of the Wisconsin Lakes, in the sum¬ 
mer season it is found in large numbers in a resting stage 
enclosed in a cocoon, hatching out in the fall. The authors 
find themselves unable to correlate this cocoon stage with 
either changes of temperature or oxygen content of the water. 
It would seem to us from our knowledge of the habits of the 
species, that it is probable that temperature will be found to 
be the controlling cause of this encystation. 
CYCLOPS LEUCKARTI Claus. 
Plate LXXIY, figs. 4-11; Plate LXXV, figs. 1-3. 
1857. Cyclops 
1863. 
1863. 
1874. 
1875. 
1876a. 
1876b. 
1880. 
1884. 
1884. 
1884. 
1885. 
1885. 
1885. 
1886. 
1887. 
1890. 
1890. 
Leuckarti Claus, p. 35, pi. I, fig. 4, pi. II, figs. 13 and 14. 
“ Sars, p. 239. 
“ Claus, p. 101. 
simplex Poggenpol, p. 70, pi. XV, figs. 1-3. 
tenuicornis Uljanin, p. 30, pi. IX, figs. 12 and 13. 
Leeuwenhoekii Hoek, p. 19, pi. Ill, figs. 1-12. 
Leeuwenhoekii Hoek, p. 132, pi. VII, figs. 1-12. 
simplex Rehberg, p. 542. 
“ Herrick, p. 150. 
oithonoides Herrick, p. 150, pi. S, figs. 2-6. 
Leuckarti Herrick, p. 146. 
“ Daday, p. 218. 
simplex Daday, p. 236. 
pectinatus Daday, p. 223, pi. I, figs. 7-13. 
simplex Vosseler, p. 193, pi. IV, figs. 15-17. 
“ Herrick, p. 17, pi. VII, fig. 1, a-j. 
“ Thallwitz, p. 79. 
“ Lande, p. 55, pi. XVI, figs. 42-45, pi. XVII, figs. 
46-50, 
