232 



DISCOVERY REPORTS 



to be present in November with a modal length of 6-3 mm. The curve for December 

 shows two modes, but this may be due to moulting or to the sampling of a different 

 brood, either a possible cause of this bimodality. A steady increase in modal length to 

 1 1 -o mm. in March takes place throughout the series. The curves for the males for 

 November and December show two modes similar to those in the female curve for 

 December and they suggest the same possible causes. The two modes, however, 

 approach and coalesce, so that a maximum growth in the length of the carapace from 

 6-2 mm. in November to 11-5 mm. in March is shown. 



40 



30 



13 

 Z 

 1^20 



u 

 < 



Q_ 

 < 



< 



u 



10- 



» X 



X X 



S t > 



5 < « 



^ z 5 



u 



UJ 



o 



2 LD K U cD tt^ 

 r> Z) D UJ LlJ ^i: 



z ^ < 



-p s = 



O cb CE 



13 I- U CD 



Fig. 13. Munida subiiigosa, males. Graph of modal lengths of curves of error drawn in Fig. ii. 



Turning now to the Falkland Islands material, the female M. gregaria makes its 

 appearance at the smallest modal carapace length of 7-0 mm. in January (Fig. 15). The 

 New Zealand specimens of this month have a carapace more than 2 mm. longer, but the 

 difference in latitude of more than 6° between Otago Harbour and the north coastal 

 waters of the Falkland Islands, whence the material was derived, explains the dis- 

 crepancy. If this smallest group were hatched from the egg in October or November the 

 larval life of this species must be much shorter than that of M. subrugosa, which first 

 appear as post-larvae in May and then at a slightly smaller length. February shows this 

 group about a mode of almost 9-0 mm., and by April it has grown to a length of slightly 

 more than lo-o mm. No increment of importance is added by May. This means a 

 growth of 3-5 mm. in the five months January to May which is rather less than the 

 growth of the New Zealand M. gregaria for the five months November to March. This 

 first-year group, in which a considerable retardation of the growth rate is apparent in 



