■ 20 G Canadian Arctic Expedition, 1913-1918 



These animals were very shy and alert when I tried to catch them, and the 

 ponds they occurred in were pretty deep in places, though the fairy-shrimps 

 seemed to prefer the shallower marginal water of the ponds, where the vegetation 

 was most luxurious. The males were bigger, but less agile than the females, 

 which of course had ripe eggs in the ovisac; in colour both sexes were as those 

 described above from Martin point. In text figure 4d is shown an outline of the 

 male genitalia; seen from the side. 



The Branchinecta paludosa collected at Young point on July 18, 1916, 

 measured from 10 to 13 mm. in length. Five of these were male and three 

 females. The latter ones were the smallest, but had a few ripe eggs in the ovisac, 

 while the males had big claspers. In colour, etc. they were the same as the many 

 specimens of corresponding sizes (age) secured at Bernard harbour, farther 

 east, in 1915 and 1916 (see below). 



At Bernard harbour, on June 17, 1916, just hatched nauplii and metanauplii 

 of Branchinecta paludosa occurred in one pond near the beach on the west side 

 of Chantry island, and in another at somewhat higher elevation on the south 

 side of the same island. Both were typical shallow tundra ponds and particu- 

 larly the one most easterly situated had a luxuriant vegetation of mosses, green 

 algae, and detritus-mud bottom. The larval fairy-shrimps were present in 

 great numbers, but somewhat difficult to observe, owing to their minute size, 

 transparency and habit of hiding among the stones (gravel) and vegetation; 

 I caught them in a similar way as I secured the larval Lepidurus arcticus in 

 Greenland (1911, p. 336), by stirring up the water along the margin of the pond. 

 I secured about 3 dozen of them altogether; and as the earliest larval stage of 

 Branchinecta paludosa was hitherto unknown I give a sketch (text figure 4e, /) 

 and short description of them (stage I). 



It will be seen from these two figures (side view and abdominal dorsal view), 

 that the nauplius eye and first pair of antennae are well developed, and that the 

 head part of the larva comprises about half the total length, and is of rounded 

 ovate shape. The second pair of antennae are enormously developed, and 

 divided into a shorter, more basal, and a longer, distal, plump branch with 

 long swimming hairs, among which are half a dozen situated at the base of the 

 biggest branch of the antennae. At the base of each antenna project two ^ long 

 stylet-spines ^ with a "brush" of small hairs at their ends, proportionately 

 longer (hairs) and more one-sided than on the larva figured by Sars (1896, pi. 

 VIII, fig. 15); we may perhaps suppose these stylets help in keeping the equil- 

 ibrum when the nauplius swims, and in the gathering of food in the succeeding 

 stages of the larva (Sars, p. 54). The largest branch of the antennae particularly 

 shows evidence of its contractile nature (joints) . There is no sign of the composite 

 eyes yet. Behind these antennae are seen the large mandibular palp, with half 

 a dozen long hairs (Sars figures eight). Then follows the somewhat pear-shaped 

 abdomen, showing indistinct segmentation (3 joints?) and by being serrated, 

 with short hairs on the ventral side indicating the foliaceous legs. It is possible, 

 that the end of the abdomen has been damaged (missing) in my specimens, 

 because it is more bluntly cut off, and does not end tapering and in two short 

 spines as in Sars' larva. There is no question, however, as to my larvae being, 

 as indicated by the length of their first pair of antennae, the rounded body form, 

 etc., nearer the just-emerged nauplius stage than is that of Sars. The youngest 

 of these larvae, which had apparently been hatched a day or two previously 

 and of which two were secured, were | mm. long, while that of Sars was perhaps 

 1 mm. long. I further secured half a dozen metanauplii (stage II) about 1 mm. 

 long, similar to Sars' figure 15 (Plate VIII), the oldest of these showing trans- 

 itions (both in size and development) to a half dozen metanauplii (IJ mm. long) 

 corresponding to Sars' figure 16. The oldest of these latter in the same way 



1 The inner one of these, which Sars (1896) says ends in a divided "brush," is very indistinct in my 

 Bpecimens. 



■Sars' "spike-bristles." 



