314 



DISCOVERY REPORTS 



neighbourhood of say Station 1 144 (although not necessarily so long before as 5 March), subsequently 

 developing to their present state during their journey from there to 0°. From 18° W to 0° the distance 

 in latitude 60° S is approximately 540 miles and although as yet little is known for certain about the 

 speed of the Weddell current, the observations of Weddell himself and of other early and recent 

 navigators^ suggest it might be of the order of between ^ and 2 knots, or say between 1 2 and 48 nautical 

 miles a day. At 24 miles a day the larvae would be carried from 18° W to 0° in 22 days, long 

 enough it might be for them to develop from the First to the Third Calyptopis stage. While again 

 nothing definite is known of the duration of this particular phase, the developmental condition of the 



MONTH 



DATE 



STATION 



FURCILIA 6 



5 



4 



3 



2 



I 



CALYPTOPIS 3 



2 



I 



IB 19 22 

 N42 N43 VII 



23 27 28 

 1492 823 VI2 



Scale per cent 

 o 50 100 



I 38 80 2653 34 379 255 1 213 — 24 24 — 



15 17 

 1965 VI4 



19 20 25 

 620 622 361 



25 



362 



♦♦ 



DEEP LARVAE | 88 80 2653 34 379 255 | 213 



MONTH 



DATE 

 STATION 

 6 FURCILIA 

 5 

 4 

 3 

 2 

 I 



3 CALYPTOPIS 

 2 

 I 

 DEEP LARVAE 



* LARVAE ABOUT TO REACH SURFACE 



Fig. 77. Developmental condition of surface larvae in Weddell West in January and February. 



For details of construction see p. 312. 



surface larvae in Weddell West in January and February (Fig. 77) suggests that it might well be 

 of this order. For in January it will be seen, from the i8th onwards, the vast majority are still in the 

 First Calyptopis stage, it being not until 17 February that in this sector the first substantial numbers 

 of Third Calyptopes are found. In northern waters (p. 119) Lebour (1924) found that laboratory 

 reared specimens of Nyctiphanes coiichii (Bell) took 15 days to grow from First to Third Calyptopes, 

 while the plankton investigations of Einarsson (1945) suggest that the same developmental phase in 

 Thysanopoda acutifrons (Holt and Tattersall) might take about 23 days. The corresponding phase in 

 Meganyctiphanes norvegica (M. Sars) might it seems be shorter, Mauchline (1959) finding that in the 

 laboratory it lasts from 9 to 12 days. 



The young, for April indeed remarkably young, surface swarm encountered in 19° E at Station 2346 

 (Fig. 76) clearly could not have come from far west in the surface drift. Like the March swarms 

 at Stations 1994, 1142 and 1144 in Weddell Middle it must have come to the surface in situ, or again 

 if not actually in situ, somewhere not far to the west of where we found it. It must have sprung, too, 

 from an oceanic spawning that took place somewhere in this far eastern sector of the Weddell stream, 

 not necessarily, however (p. 304), near the site of Station 2346. 



To continue the discussion on the March-April distribution of these surface forms it will be seen 

 that although the region is otherwise virtually barren there is a single although substantial March 

 occurrence of Calyptopes on the South Georgia whaling grounds. Their situation to the south-east of 



1 In the track chart illustrating his great southern journey of 1823 Weddell records a maximum speed for the surface drift, 

 a little to the west of 30° W, of 21 nautical miles a day, while farther west, off the east coast of Graham Land, Larsen in 

 December 1893 reported north-easterly and north-north-easterly sets of from i to 2 knots (Murray, 1894). Near the South 

 Orkney Islands {Antarctic Pilot, 1948) easterly sets of | knot are common and settings to the east of as much as i^ knots 

 have been reported. Bruce (1918) records an easterly set of 35 miles in 2 days in Weddell West, Wordie (1921 b) stating that in 

 this part of the current the pack travels towards the South Orkneys 'often as fast as 20 miles a day'. In the straits and narrow 

 passages of the South Orkney Islands themselves the strong, 3J-4 knot, tidal currents reported by Powell (1822) and the 

 tide-rips reported by ' Discovery IT (Marr, 1935) in January 1933 provide, it seems, further evidence of the strength of the 

 Weddell stream as it sweeps eastward through the group. 



