6 e Canadian Arctic Expedition, 1913'18. 



4. February 18, 1916. Ice 6 feet. Common. 



5. May 6, 1916. Ice 7 feet. Temperature of surface water 32-5° F. 

 Few. Young ones emerging from mother-animals. 



6. May 21, 1916. Temperature of surface water 33° F. Young and adults, 

 young in upper water, and older ones between 12 feet and 20 feet. 



7. June 12, 1916. Ice 6 feet. Temperature of surface water 33° F., air 

 38°. Young and adults common'. 



Bosmina longirostris (0. F. Mueller). 



This species appeared only in the material collected in the two big lakes 

 (see fig. 3) at Bernard harbour, Northwest Territories. It was obtained on the 

 following dates: — 



F. Johansen, photo. 

 Fig. 3- — Big lake at Bsrnard Harbour, Northwest Territories, August, 1915. 



1. September 26, 1915. Ice 7-5 inches, depth of the water 9 feet. One 

 female. 



2. September 30, 1915. Ice 8 inches, depth of water 19 feet. Common, 

 about a quarter of the specimens with embryos in brood chamber. 



3. November 28, 1915. Ice about two feet. Temperature of the water at 

 surface 32° F'., below surface 32-5°. Few. 



4. February 12, 1916. Ice 5 • 5 feet, depth of water 20 feet. Temperature of 

 the water at surface 32° F. Very few. 



5. June 12, 1916. Ice 6 feet. Temperature of surface water 33° F., air 

 38°. Few. 



Eurycercus glacial is Lilljeborg. 



This species is one of the largest forms among the Cladocera. Some indi- 

 viduals reach a length of 6 mm., but in most instances they do not exceed 5 mm. 

 As many as forty summer or parthenogenetic eggs have been found in the brood 

 chambers of the larger females. 



Several specimens 5 mm. long were noted in this material, but none exceeded 

 this length. This form appeared in five plankton samples : — • 



1. August 3, 1913. Teller (Port Clarence) , Alaska. Brackish pond between 

 big lake and sea. Abundant, various sizes, some full grown with summer eggs. 



2. August 14, 1914. Herschel island, Yukon Territory. Pond on east 

 end of island. Elevation about 250 feet. Much vegetation. Several adults 

 5 mm. long as well as smaller individuals. 



