Crustacean Life N 5 



the middle of October) \ and the sea generally freezes over rather suddenly 

 about the middle or end of September, though open water lanes may be seen 

 offshore here and there all winter. 



The appearance of the ponds, lakes and lagoons upon the coastal plain 

 of Arctic Alaska is practically the same everywhere all the way to the Mackenzie 

 delta, and the accompanying photographs (Plate I) show them better than 

 many words.^ Nearest the beach the low, gravelly or tundra-coast often forms 

 smaller or larger lagoons more or less connected with the sea. Where the water 

 from the latter has access to the lagoon at high tide, it contains neither 

 phyllopoda nor cladocera, though copepoda, fish fry and certain insect forms 

 are found; but when it is really a beach-pond separated from the sea by drift- 

 wood, sand, and gravel sometimes with vegetation it contains at least some of 

 the other Crustacea too. In all cases the Water is more or less brackish. The 

 lagoons and beach ponds examined in June, 1914, at Martin point and in 

 Camden bay (Konganevik and Collinson point), Alaska, are typical in regard to 

 this. 



At Martin point the investigations were made at the end of July^ and all 

 the lagoons and beach ponds seen there although extensive were very shallow 

 (maximum depth of six inches). One lagoon pond had a water temperature 

 of 52° F. at 3 p.m. (air 34" F.), on July 28. Its bottom was black, sandy mud, 

 overlaid by a layer of light brown detritus mud and with loosely lying masses of 

 green filamentous algae, etc. The macroscopic life consisted of a great many fry 

 of the sculpin Oncocottus quadricornis, red Chironomus larvae* in their mud-tubes, 

 and various copepods (Eurytemora sp., and Canthocamptus sp.,) besides collem- 

 embola and small diptera on the surface. Even the lagoons that were connected 

 with the sea at high tide had this same animal life. Another lagoon pond had 

 more the character of a true beach pond. Its water temperature was 51° F. at 

 10 a.m. (air 32° F.) on July 26, and the bottom consisted of gravel, sand and, 

 especially on the deeper places, fine light brown detritus mud, such as is usually 

 formed by the Chironomus tubes and excrements. The insect life consisted of 

 the usual collembola and small diptera upon the surface, and dytiscid beetles 

 and larvae besides small dipterous larvse in the water. Far more conspicuous 

 and interesting, however, were the freshwater crustaceans it contained. Besides 

 the usual copepods (see above) I noticed and collected a great many Daphnia 

 pulex of different sizes (see Report of Canadian Arctic Expedition, "Vol. VII, 

 Part H), besides the two characteristic arctic phyllopods, Lepidurus arcticus 

 and Branchineda paludosa. The former were making their familiar, winding 

 tracks in the mud bottom, buried at the one end, or "browsing" immediately 

 above it. In size they were from 8 to 18 mm. lorg (excluding the cercopods), 

 thus probably representirg both this and the preceding year's brood; all were 

 females. Swimming around in the water were also fairy shrimps (Branchin- 

 eda paludosa) of both sexes from 1| to 2 cm. in length; they were extremely 

 active, swimming briskly around and trying to bury themselves in the mud, as 

 I fished for them. The females carried ripe eggs and had much more briUiant 

 colours than the paler males. 



Similar shallow lagoons and beach ponds cut off from the stream-outlets 

 by sandbars and partly dried up, and with stagnant and brackish water, were 

 noticed at Konganevik in Camden bay in the end of June, 1914, but I found no 

 Entomostraca in them, though they contained fish fry^ and the usual insect life 



1 On September 20, 1913, this ice was six inches thick. (Observations at Collinson point.) 



2 See also Plate VI . in Brooks: Geography and Geology of Alaska (1906) ; Plate II. in Schrader and Peters : Recon- 

 naissance in Northern Alaska, Washington, 1904, (Prof. Papsr, No. 20, U.S.G.S.); Plates III. -V. in Leffingwell: Canning 

 River Region Northern Alaska, Washington, 1919, (Prof. Paper, No. 109, U.S.G.tj.) ; and the marine chartF published by 

 the British Admirality and the U.S. Hydrographio Office (also Alaska- Yukon Boundary Survey Map.) 



3 In this report "Beginning" of a month means 1st to 10th. 



" " "Middle" " " 11th to 20th. 



" " "End" " " 21st to 30th (31). 



* For aquatic insects see Vol. Ill of this series of reports. 

 6 Oncocottus quadricoTnia, 



