The Cladocera of the Canadian Arctic Expedition, 1913-18. 



By CHANCEY JUDAY. 

 Wisconsin Geological and Natural History Survey. 



The plankton collections secured by Mr. F. Johansen during the Canadian 

 Arctic Expedition are of particular interest from the standpoint of the geo- 

 graphical distribution of the Cladocera because they were obtained from a 

 region in which collections had not been made previously. These entomostraca 

 had been collected in Greenland and in Labrador oh the east and in Alaska on 

 the west, but the intervening region of Arctic North America was represented 

 only by a single small collection; some freshwater plankton was collected at 

 Fiillerton, Northwest Territory, on the west side of Hudson bay, during the 

 Neptune Expedition of 1903-4 an,d this material contained a single cladoceran, 

 namely, Daphnia pulex (de Geer). 



The present collections contain representatives of seven species of fresh 

 water and two species of maririe Cladocera. All of these species are well known 

 and they have a wide range geographically; with one exception they are widely 

 distributed not only in high Arctic latitudes but also in the north temperate 

 zone. Eurycercus glacialis, as far as known, is confined to the Arctic regions. 



The United States National Museum kindly loaned its collection of American 

 Arctic Cladocera, and the two species of Daphnia represented therein have been 

 included in this report. 



FRESH WATER CLADOCERA. 

 Daphnia pulex (de Geer). 



This species is cosmopolitan and circumpolar in its distribution. There are 

 several varieties, at least two of which are represented in these collections. 

 According to Lilljeborg, the species shows seasonal variations in its form, and the 

 same appears to be true of this Canadian material. 



The typical form of this species is most abundant in the collections. Speci- 

 mens of the animal or of its ephippia were noted as follows: 



1. August 6, 1913. Teller (Port Clarence), Alaska. Ponds on higher 

 tundra between big lake and sea. Few, various sizes. 



2. June 4, 1914. Collinson point, Alaska. WaterhoJe on tundra. 

 Ephippia. 



3. June 25-26, 1914. Konganevik (Camden bay), Alaska. Margin of big 

 lake among vegetation. Ephippia. 



4. July 11, 1914. Collinson point, Alaska. In waterhole at beach, no 

 vegetation. Temperature of water at 6 p.m., 58 F. Young, just hatched. 



5. July 26, 1914. Martin point, Alaska. Big brackish lagoon about one- 

 half foot deep, rio vegetation. Temperature of water at 10 a.m., 51 F. Many, 

 all sizes from newly hatched to full grown with parthenogenetic eggs. 



6. August 14, 1914. Herschel island, Yukon Territory. Pond on north- 

 east end of island. Abundant, some with ephippia or winter eggs. 



7. June 25, 1915. Bernard harbour, Northwest Territories. Lakes and 

 ponds on tundra, inland. Much vegetation. Many ephippia. 



8. July 8, 1915. Locality, etc. as preceding. Young and ephippia. 



9. July 15, 1915. Bernard harbour, Northwest Territories. Brackish 

 pond near creek outlet. Large numbers of young, but none quite full grown. 

 Enormous numbers of ephippia attached to filaments of algae. 



10. July 19, 1915. Bernard harbour, NortHwest Territories. Brackish 

 pond near creek outlet. Many. 



