Cyclops. 



215 



Cyclops serrulatus Fischer. 



1838. 



1851. 



1853. 



1857. 



1863. 



1863. 



1863. 

 1870. 



1872. 

 1875. 

 1878. 

 1880. 

 1882. 

 1883. 

 1884. 

 1885. 

 1886. 

 1891. 

 1891. 

 1891. 

 1892. 



Plate VI, figs. 2-5. 



C. agilis Koch (3), H 21, pi. III. 



serrulatus Fischer (5), p. 423, pi. X, figs. 22, 26-31. 



Lilljeborg (6), p. 158, pi. XV, fig. 12. 



Claus (7), p. 36, figs. 1-3. 



Sars (11), p. 45. 



Claus (9), p. 101, pi. I, figs. 1 and 2; pi. 

 IV, fig. 12 ; pi. XI, fig. 3. 



Lubbock (10), p. 197. 



Heller (12), p. 6. 



Fric (13), p. 222, fig. 18. 



Uljanin (15), p. 34, pi. VIII, figs. 1-8. 



Brady (18), p. 109, pi. XXII, figs. 1-14. 

 agilis Rehberg (19), p. 545. 

 serrulatus Herrick (23), p. 230. 

 pectiriifer Cragin (24), p. 6, pi. IV, figs. 1-7. 

 serrulatus Herrick (26), p. 157, pi. O, figs. 17-19. 

 agilis Daday (27), p. 240. 



agilis Vosseler (28), p. 190, pi. V, figs. 29-31. 

 serrulatus Schmeil (37), p. 29. 



Brady (36), p. 18, pi. VII, fig. 1. 



Richard (39), p. 234, pi. VI, fig. 19. 



Schmeil (41), p. 141, pi. V, figs. 6-12. 



C serrulatus is found everywhere. It is the most common of 

 all the species of Cyclops. In the larger bodies of water it is 

 more common in littoral collections, but it occurs not infre- 

 quently in pelagic collections. 



This species has a wide limit of variation, the extreme forms 

 differing so much that one is at first inclined to rank them as 

 separate species. At one extreme is the form common in ditches, 

 pools, and littoral collections, which seems to correspond nearly 

 to montanus Brady. It averages .85 mm in length; the furca 

 is not quite as long as the last two abdominal segments, and 

 the external terminal seta is transformed into a stout spine 



