248 



DISCOVERY REPORTS 



MONTH 

 lOO 



MAR SO- 



too- 



MAR so 

 lOO- 



FEB SO 



-lOO- 



FEB SO 

 lOO 



MAR 50- 

 lOO 



FEB SO 



-lOO 



APR SO 



8 12 16 2024 28 32 36404446 52 566064 



STATION 

 368 



-lOO- 



APR SO- 



-lOO- 



FEB SO- 



lOO 



FEB 50- 



MONTH 



38 



351 



354 



24 



352 



42 



207 



618 



622 





STAGE $ 



2 3 4 5 6 7 



— 1 — 1 — r-1 — 1 — r 



J 

 i 



1 — ; — I — r 



1 I I I — I — r 



-I — 1 — 1 — r 

 2 3 4 S 6 7 



STAGE cf" 



12 3 4 5 6 7 



T — I — I — I — I — I — r 



-^ — I 



-^ — I 

 I — r^^^T*- 

 r^ — I — 



-^ — I — r 



"1 — I I I I — I — r 

 I 2 3 4 5 6 7 



J 



1 I I I — I — r 



i 



4 





1 — I I I I I I 



M 



1 1 I 1 1 1 r 



J 



1 I I T" 



8 12 16 2024 28 32 3640444852 566064 



I 2 3 4 5 6 7 



fe. 



STAGE 9 



2 3 4 5 6-^ 



STAGE cT 



LENGTH RANGE 



Fig. 5 1 . Sexual dimorphism and developmental condition of the sexes in swarms of E. superba, showing growing 



dominance of the male (Continuation of Fig. 50). 



Relative size of the sexes 

 In her growth curve illustrating the average monthly length of the larvae, adolescents and adults 

 Bargmann ( 1 945 , p. 1 29, Fig. 3) shows that from the earliest stage at which the sexes can be distinguished 

 (when the krill have reached the Sixth Furcilia stage) the females are consistently, if only slightly, 

 smaller than the males. Using largely the measurements given in Table 19 of her appendix an attempt 

 has been made in Figs. 50-52 to illustrate this slight measure of sexual dimorphism in so far 

 as it can be expressed in terms of the length frequencies of the sexes that have been recorded in our 



