LARVAL DEVELOPMENT 



213 



of New Zealand M. gregaria kept under observation in captivity. The catches of M. 

 gregaria were, however, scanty in November and December, and the conclusion that 

 this definite spawning season occurs would be unwarrantable were it not supported by 

 the frequency of Mumda larvae in the plankton during September and October and by 

 Young's observation. 



50- 

 40- 

 30- 

 20- 

 10 

 



MUNIDA GREGARIA 



SEPT OCT NOV DEC JAN FEB MAR APR MAY 



Fig. I . Percentage of berried females to total catch of females in Munida subrugosa and M. gregaria. 



Berried females again appear in the January and February catches in increasing 

 numbers, but a fall occurs in March and April. It seems probable that females are 

 again beginning to bear eggs after spawning in September and October, but that the 

 hauls made in March and April, in which the catches of M. gregaria were only small, 

 have failed to sample this part of the population. 



Should spawning take place in September and October — which seems certain — and 

 should eggs be extruded on to the pleopods in January and February — which seems 

 probable — a period of eight months must be assigned to egg-carrying on the part of the 

 female, a length of time which may be compared with ten months in the case of the 

 American lobster, Homanis americamis (M.-Edw.), Herrick (1895). 



In these circumstances, unless several months or a whole year are passed without 

 breeding, the adult female can seldom, if ever, undergo more than one moult per year, 

 the moult taking place between the time of hatching of the eggs and the resumption of 

 egg bearing, i.e. October to January. The probability that long resting periods elapse 

 between successive reproductive phases in the individual is upheld by the low per- 

 centage of berried females to the total population at any time. Such resting periods 



