32 PROCEEDINGS OF THE ACADEMY OF [Jan., 



accounted for by the strongly arched cephalothorax of C. albidus, 

 which enables the animal to place the fifth feet close upon the first 

 abdominal segment. In C. fuscus the shorter basal segment is 

 frequently only a foreshortening because of the angle at which the 

 feet are held. The arrangement of the spinules, the spines and the 

 setae are exactly as in C. alhidus (PL I, fig. 13). 



The receptaculum seminis (PI. I, fig. 11) consists of two main 

 divisions. The anterior portion is wide, shaped very much like the 

 corresponding portion of the receptaculum in C. alhidus, but with a 

 very distinct indentation on its anterior border. The posterior 

 part appears as a pair of slightly elongated reniform divisions sepa- 

 rated by a median line and fusing at the porus. The color of the 

 receptaculum is always a deep reddish-brown which frequently makes 

 it difficult to distinguish its outline. 



The egg-sacs are carried very close to the abdomen. The eggs 

 are dark; in the living animal they look quite black, but in reality 

 they are a deep shade of brown. This applies only to freshly de- 

 posited eggs, as all Cyclops eggs from which the young are about to 

 emerge show a characteristic salmon tinge due to the color of the 

 bodies of the nauplius. 



The length of the female varies but little. The following five 

 measurements ^ve an approximate average for C. fuscus from this 

 locality. All measurements include the caudal setae. 



No. 1 3.75 mm. 



No. 2 3.2 mm. 



No. 3 3.4 mm. 



No. 4 3.4 mm. 



No. 5 : :3.58 mm. 



Average 3.46 mm. 



Schmeil gives 3.4 mm. Brewer's figures are much smaller — 1.4 mm.- 

 1.8 mm. The males are often only half as long as the females. An 

 average length is 1.75 mm. 



The color of the first four thoracic segments and the abdomen 

 from the posterior half of the first segment to the furca is usually a 

 dark green. The fifth thoracic segment, the stylets, and the fourth, 

 fifth, twelfth, thirteenth, and fourteenth segments of the first antennae 

 are blue. The anterior half of the first abdominal segment is reddish- 

 brown. Occasionally there are irregular blotches and streaks of 

 blue on the posterior borders of the first four thoracic segments. 

 The remaining segments are a dirty yellow color, deeper on the 

 anterior border. 



