194 



males there are only 62 soft females. This points to the 

 fact that the mature males oast more often than the 

 females. It is probable that both males and females of 

 between four and a quarter inches and six inches cast once 

 in two years, so that it is in the older crabs that the males 

 cast more frequently than the females. I do not attach 

 too much importance to the above figures, as the numbers 

 are too small to justify their use in the question of the 

 frequency of casting. So far as they go, however, they 

 confirm my statement that the female crabs over six 

 inches do not cast so often as the males of a similar size. 

 It is, therefore, probable that the " granny " crabs are not 

 diseased, but are merely females ready for casting. They 

 are only found amongst females of over six inches in 

 breadth. The reason why smaller females and males of 

 all sizes do not become " grannies " is because they cast 

 at least once in two years. 



I have been unable to find any reference to 

 " granny " crabs in the literature* of the subject, but 

 Williamson says " as a rule the shell of the old female 

 crab is much more dirty than that of the male."t He 

 attributes this dirtiness to the fact that the female when 

 carrying eggs lies half buried in the mud. This explana- 

 tion may have some truth in it, but it does not solve the 

 problem as to why only female crabs above six inches in 

 breadth become discoloured. 



It is evident that the various processes which are 



characteristic of the life-history of the edible crab are 



subject to considerable variation, and it is necessary that 



further investigations should be made before the numerous 



problems can be regarded as being solved. 



* With the exception of a preliminary notice by Professor 

 Herdman in Twenty-first Annual Report of the L.M. B.C. (Port Erin 

 Marine Biological Station), p. 25. 



f Williamson. Eighteenth Report, p. 110. 



