RHINCALANUS GIGAS 



321 



earliest nauplii to be hatched, since naupHi never made their appearance at any sub- 

 sequent time during the season, and, as will be seen (pp. 326, 328), young copepodites 

 were taken at the end of the first week in January. It is thus at least evident that a very 

 short time, perhaps not more than a week, elapses between the shedding and hatching 

 of the eggs. 



It will be seen from Table V a-c that the proportion of males is almost always higher 

 in the deep nets (250-100 m.) than in the shallow hauls (loo-o m.). At many stations 

 where males occurred in the lower haul none was taken at all in the upper net, and, 

 during the maximum period for adult males, the percentage of them in the upper nets 

 underwent no increase. It is evident that adult males are more restricted in vertical 



96 



40- 



30 

 20 



I OH 



is 



-■er' 



,xi 



/ CX x^ 



xO 

 O 



X SEASON 1931-32 

 O SEASON 1932-33 



XD-. 



% 

 40- 



30- 



20- 



10- 



10 15 20 25 

 OCTOBER 





>S< 



■-0---- 



5 10 15 20 25 

 NOVEMBER 



ID 15 20 25 

 DECEMBER 



— iX'ilT , 1 rX 



5 10 15 20 25 

 JANUARY 



X 



5 10 15 20 25 

 FEBRUARY 



G 



10 15 20 25 

 MARCH 



10 15 20 25 

 APRIL 



10 15 20 25 

 MAY 



10 15 20 25 

 JUNE 



ID IS 20 25 

 JULY 



Fig. 18. Rhincalanus gigas. Adults. Percentage of males in total adults (upper and lower hauls combined). 

 Falkland Sector, 1931-2 and 1932-3 and Indian Ocean Sector, April 1932. 



distribution than females, which occurred in equal abundance in both nets. Paulsen 

 (1909) found the adult males of Colatms finmarchiciis at greater depths than the females, 

 and Stormer (1929, p. 25) wrote: " The adult (C finm.) female occurs for the most part 

 at 100-50 m. or scattered throughout all depths. The adult males arefoundat 300-50 m." 

 Male copepodites of Rhincalanus gigas in stage v are nevertheless found equally abun- 

 dantly in both nets, so that restriction to layers below the loo-m. level is peculiar to the 

 aduh. If this is the case then only those females which are below the loo-m. level during 

 the summer time will be fertilized. Nauplii and young forms, as Stormer found for 

 Calanus finmarcJiicus, are taken at the surface, so that either the fertilized females must 

 rise to the surface to shed their eggs or the eggs must rise to the surface after they are 

 shed. The curves showing the composition of the Rhincalanus stock in stages, to be 

 studied in the following sections of this paper, perhaps hint that the adult females 



