566 PROCEEDESTGS OF THE NATIONAL MUSEUM vol. lis 



of E. arctica were captured from the thick beds of Arctophila that 

 extend out into the lake (water depth, 1.0-1.5 meters) than in open 

 water (see above, p. 563) — in contrast to rehitively few individuals 

 of the other calanoid copepods. Although the data are not as exhaus- 

 tive as is desirable, we believe it reasonable to assume that the popula- 

 tion of this lake is localized in the Arctophila beds. In the Noatak 

 River pond, the species was likewise collected among weeds but not 

 from open water. Other records of occurrence contribute little to the 

 question of localization in weed beds. The vegetation of the pond at 

 Umiat, from which fanly large numbers were taken, is unknown, but 

 the method of collecting precluded sampling of both the deepest open 

 water and thick weed beds, while not excluding thinly developed 

 littoral growths. Excepting Lake 4, none of the bodies of water in the 

 Cape Thompson region were sampled adequately or frequently 

 enough to determine the absence or the preferences of a highly localized 

 or rare species. 



It is reasonable to suggest from the available data that the popula- 

 tion of E. arctica in Lake 4 is monocyclic and overwinters as resting 

 eggs, rather than as adults or late copepodid stages, as is probably 

 true for many other calanoid copepods in shallow bodies of fresh 

 water on the Ai'ctic Slope of Alaska (Wilson and Tash, MS.). Data 

 are not conclusive because the localized habitat was not adequately 

 sampled for a critical study of the life cycle, and the suggestion 

 originates from these observations: (1) littoral and open-water samples 

 of late spring-early summer in 1960 and 1961, during and after thawing, 

 had neither adults nor late copepodid stages; (2) copepodid stages 

 found in 1960 showed seasonal progression from early to adult stage, 

 and developmental stages were not collected after adults had become 

 established; ^3) samples from the deep, open waters taken under ice 

 in January 1961 (ice depth, 1.22 meters) and in April when ice depth 

 was greatest (1.75 meters) contained no Eurytemora of any stage. 



The weedy portion of the lake in which the population is presumably 

 established is of such depth (1.0-1.5 meters) that it freezes to the 

 bottom by the end of winter (April) so that copepodid stages would 

 not sm'vive dming the winter. It should be noted also that no 

 specimens were collected in open water after September 14, 1960, 

 although other calanoids were present in samples taken until Novem- 

 ber 7. Presumably, reproduction takes place in the Arctophila bed, and 

 overwintering resting eggs would be deposited there. The only indica- 

 tions of dates of breeding and egg production were late in the season 

 (August 21, 27, and September 8) when males with spermatophores 

 on leg 5 and females with ovisacs were taken in Lake 4 and nearby 

 pools, and in Lake 9. 



Field studies on coastal pool populations were too few to supply 



