60 BRITISH COrEPODA. 



between the 18th and 19th joints. The posterior 

 antennae, the mouth-organs, and swimming feet present 

 no marked characters. The fifth pair of feet in the 

 female (figs. 10, 11) are alike on both sides, consisting 

 of a rudimentary one- or two- jointed inner, and a 

 much larger three- jointed outer branch. The inner 

 branch bears three apical spines of variable size, but 

 never very large ; the outer branch has the basal joint 

 very large, the second joint small, and the third in the 

 form of a broad sword-like spine attached toward the 

 inner side of the limb ; the second joint bears in addi- 

 tion two small apical spines or setae; both branches 

 are nearly straight. In the male (fig. 9) the foot of 

 the right side is much larger than that of the left, and 

 terminates in a long, curved claw ; the inner branch is 

 in both feet quite rudimentary. The last thoracic 

 segment in the female (fig. 12) is produced downwards 

 at each side into a conspicuous sharply spined process; 

 in the male (fig. 13) it is distinctly angulated, but 

 has no conspicuous spine. The abdomen consists in 

 the female of 3 and in the male of 5 segments ; the 

 caudal segments broad and short; terminal setae 

 strongly plumose, and about half the length of the 

 abdomen. The eye is large and movable, and of a 

 brilliant red. The colour of the animal itself is very 

 variable ; yellowish, red, bluish-green, or brown ; once 

 I have seen it so red as to look like scraps of ani- 

 mated sealing-wax when swimming in the water. In 

 some cases the ovisac is of a different colour from the 

 rest of the animal. Length -^ to i^-th of an inch (1*3 

 to 2*1 mm.). 



