RHINCALANUS GIGAS 329 



the northern hemisphere the rapidity of growth of the summer generation of copepods 

 has frequently been commented upon. Ruud (1929) found that about seven weeks 

 elapsed between the maximum for nauplii and the maximum for adults of Calanus 

 finmarchkiis off the coast of Norway, and gave about three months as the time required 

 for the complete life cycle, including the embryonic development. Lebour (1916), from 

 Crawshay's cultures at Plymouth, gave only two months from the egg to stage v. The 

 population at Sts. 796, 802 and 803 had drifted probably from the region of South 

 Georgia in the West Wind Drift (Bellingshausen Sea current) since spawning. At all these 

 stations (778, 796, 802 and 803) it will be noticed that the old parent generation was found 

 in the lower nets. The greatest number of the old generation was taken at St. 778 ; fewer, 

 with some of the new generation stage iv, at St. 796 ; more stage iv and fewer of the old 

 generation at St. 803, and very few of the old generation at St. 802. Thus the old generation 

 appeared to die out as it became carried away from South Georgia. It may also be noted 

 that the stock at St. 803 in the surface haul was slightly older than the stock at either 

 Sts. 796 or 802. It contained more stage iv and fewer stage ii and must be supposed to 

 have been spawned slightly earlier than the stock at Sts. 796 and 802. St. 803 lay be- 

 tween the 2'0 and 3-0° isotherms, while Sts. 796 and 802 lay between the i-o and 2-0° 

 isotherms. It looks, therefore, as though spawning had taken place somewhat earlier in 

 warmer water (2-0-3 -0°) than in the colder water (i •0-2-0°). 



We have now a picture of the spawning of Rhincalanus gigas taking place in this 

 season in the Bellingshausen Sea current in South Atlantic water east of South Georgia 

 probably in the first fortnight in December. No spawning seems to have occurred west 

 of the island at this time, since at St. 788, taken west of South Georgia in the third week 

 in December (Figs, i a, 20), a maturing stock was still found with no young forms at all. 

 The spawning apparently took place earlier in water warmer than 2-0° C. than in water 

 with a temperature lower than this. 



It appears that the spawning took place in Antarctic water, since at St. 776 (Figs. la, 20) 

 in the sub-Antarctic zone the population at this time consisted of stages iv, v and vi 

 with no trace of a new generation. It is hardly possible that the high proportion of 

 stage iv in the surface net at this station can represent the product of a recent spawning 

 since almost no stages younger than this were found and the remainder of the stock 

 consisted of stages v and vi. At St. 775, eighty miles farther south on the Antarctic side 

 of the convergence, the population also consisted of the old generation in stages v and vi. 

 It is perhaps worthy of note that evidence of spawning was found at the stations in the 

 area where Antarctic water from the Bellingshausen Sea comes into contact with water 

 from the Weddell Sea, but that no trace of spawning was found at this time in the same 

 water away from the influence of the Weddell Sea (Sts. 774, 775 and 788). As will be 

 seen later (p. 334) there was found in February between the Falklands and South 

 Georgia a very scanty population on the sub-Antarctic side of the convergence in 

 stage iii, which was judged to be the result of a very greatly diminished spawning 

 which took place in sub-Antarctic water much later than the main spawning in 

 Antarctic water. 



