BYRNES: CYCLOPS OF FRESH \VATER. 



Armature of adult C. brevispinosus. 



17 



Foot No. 



Ramus, Outer or Inner. 



I 



II 



HI 



IV 



O 



Outer Spines 3 



Apical Spines 



Apical Setiy 2 



Inner Seta; 2 



iseta. 



The fourth foot of an adult C. brevispinosus- (Fig. 2, Plate X'lL), 

 sometimes bears one spine and one seta on the apex of the outer 

 ramus in place of two spines. The fifth foot is shown in Fig. 3, 

 Plate VII. This species agrees with C. parens in the form of the 

 receptaculum seminis, and also in the labrum which carries nine 

 small teeth between two tooth-like projections of the onter angles, 

 making a total of eleven teeth. 



Herrick clearly recognized the difiference between C. parens and 

 C. breiispiuosiis. Forbes also in discussing the members of the 

 viridis group recognized the stable characteristics of brevispinosus 

 and concluded that "Brevispinosus should be considered a good 

 variety, " /. e., of C. viridis. 



Heterogenous-'' Form of C. Brevispinosus. — Side b\- side with 

 C. parens, C. Americanns, Marsh, and C. brevispinosus, is fre- 

 quently found a Cyclops of very similar appearance. It is sexually 

 mature and agrees with C. parens in having two outer s])ines on 

 the terminal segments of the outer rami of the swimming feet 

 but it differs from C. parens in the constant occurrence of a well 

 formed spine on the outer margin of the inner ramus of the fourth 

 swimming foot, where there is a se/a in C. parens. The segments 

 of the outer ramus of the fourth foot of this Cvclops are shown 

 in Fig. 7, Plate \TI. 



The entire armature of this Cyclops in the "parens stage" is as 

 follows : 



■'' The term Iictcrogciiy is used here to denote the existence of two adult 

 forms which represent successive generations, botli of which are sexually 

 mature, but morphologically unlike. 



