12 G Canadian Arctic Expedition, 1913-1918 



sory claspers" are also armed with "teeth" (spine-hooks), and there may be 

 some seasonal and local variation as to their fusion with the rest of the antennae. 

 It is, therefor, perhaps not so surprising, that they were overlooked in Murdoch's 

 more superficial description of the male. His figure (4a) is also very poor. The 

 foliaceous legs of this species are described by Murdoch as short and broad, and 

 are very similar to the foliaceous legs of the other known species (P. judayi) 

 figured and described by Daday (fig. 3d, e, /,; p. 110, 1910); so I can pass right 

 on to the abdomen of the male (text figure 26). The ventrally protruding 

 genitalia of my specimens are plump and sack-like,^ their free ends (penis) being 

 almost horse-shoe shaped, and armed with small spines along their edges and on 

 the more bluntly cut off end. There seems to be a great number of segments in 

 the tail (abdomen), but probably it is somewhat contracted, the (eight?) joints 

 being telescopically compressed at the distal end, so there seems to be ten seg- 

 ments. The cercopods are a little smaller than with the females. 



Three days later (August 6, 1913) I collected six females of this same 

 species in another pond situated on the tundraplateau nearby, at Teller, Alaska. 

 I give here (text figure 3) an outline of the head and tail-end of the biggest of 

 these six females. It will be seen, that the frontal, lamellar process is less con- 

 spicuous than in the male, though the nauplius-eye is as distinct; on the other 

 hand, the first pair of antennae. are more prominent, as is also the brain and 

 adhesive organ behind the nauplius eye. The second pair of antennae are only 

 developed as two conical protruberances, slender and finger-like at their tips. 

 The labrum seems to be larger than with the male, and has very much the same 

 outline as the frontal process of the other sex. The abdomen is less tapering, 

 but more swollen and longer than with the male, owing to the development of 

 the large ovum-sack, which has obliterated several of the segmental distinctions, 

 so there are only half so many (but longer) joints here than with the male. The 

 dorsal view shows how the ovisac is "protected" dorsally by 2 broad flaps (folds) 

 apparently continuations from the last body-segment and the first ones of the 

 abdominal segments; and the ventral view shows 2 finger-like processes one on 

 each side of the uterine opening, the latter being large and lanceolate in shape 

 supported inside by a broad, circular "rim."- From the ventral view the ovarium 

 is also seen to be enclosing the intestine as an almost solid mass, only separated 

 in two at the middle. Half a dozen ripe eggs appear on each side of the ovarium. 

 Murdoch did not notice the two abdominal, dorsal flaps, though he records the 

 two slender ("tooth-like") processes beside the ovarial opening, and the volumin- 

 ous ovisac, rounded at the end. In my specimens the egg-sac is about two- 

 thirds the length of the abdomen, and of a swollen-conical shape. The cerco- 

 pods seem to be somewhat longer and broader than with the male; and there 

 are 17 pairs of foliaceous legs. Length of head 1 mm.; of body 7 mm.; tail 

 4 mm. (including cercopods). 



The five other females are a little smaller, about 10 mm. long, to end of the 

 cercopods, but otherwise as developed. 



The sexual differences in this species are thus very distinct, and comprise, 

 in addition to the different development of claspers and genitalia, a more plump 

 shape ,of the male, owing to its smaller size ' and shorter but more jointed 

 abdomen, characters which are also found in the other species (P. judayi) 

 of this genus, and in the Eurasian species Polyartemia forcipata Fisch., belonging 

 to the same family (see Sars, 1896, p. 60-62). 



The females of Polyartemialla judayi are very similar to those of P hazeni; 

 but the males are immediately recognized, their claspers being more in the 



^ Daday figures (2(1) and mentions (p. 106) a fingerlike short process protruding from the middle of 

 the ventral surface (Copied from Ekman). 



2 On one of Daday's (Ekman's) figures (2 b) is also seen a " wing-flap " on each side of the egg-sack, 

 in front, and there is only one, broad fold upon the dorsal side. 



' Daday (IfllO) gives the total length of the males as 9-11 mm., and of the females as 10-12 mm. 



