VARIATIONS IN FORM AND SIZE OF CYCLOPS BREVI- 
SPINOSUS HERRICK AND CYCLOPS 
AMERICANUS MARSH. 
BY HARRIET LEHMANN. 
This investigation was undertaken under the direction of 
Professor CL Dwight Marsh of Ripon College, to determine 
the extent of variation in C. brevispinosus Herrick and C. amer- 
icanus Marsh, particularly with reference to the question of 
specific distinction between these forms in the form and meas¬ 
urements of the furca, and the outer terminal spine of the 
furca, and in the armature of the terminal joint of the inner 
ramus of the fourth swimming foot. 
The results obtained cannot, however, be considered con¬ 
clusive, since the number of specimens examined was insuffi¬ 
cient to permit exact conclusions. The variations were also 
found to be so wide in a, small number of specimens that even 
greater variation might be possible in a, large number. 
Different investigators do not agree as to the characters of the 
genus Cyclops important for specific distinction. Brady, J 78, 
gives, “the characters of the first antennae and fifth pair of feet. 
As offering subsidiary characters;, the spinous armature of the 
swimming feet, together with the tail segments and setae, are 
also important.” S'chmeil, ? 92, says, “Die sichersten und 
einfachsten Erkennungsmerkmale sind das rudimentare Eiis- 
schen und der Bau des Receptaculum seminis. * * *Die 
Anzahl der Borsten und Domen ist. fur die Individuen einer 
Art durchaus nicht konstant, so das allien heira,ufgegriindete 
Arten hinfallig werden. Hiermit soil natiirlichi nicht ausge- 
sprochein sein dass die Beriicksichtigung der Bewehrung der 
