SEA-FISHERIES LABORATORY. 



483 



These conditions do not affect the male. In the 

 female the casting time is of double importance, as it is 

 at that period that fertilisation is effected. In the male, 

 however, ecdysis would appear to be important only as a 

 period of growth. It appears to me, therefore, from an 

 examination of all the evidence obtainable, that male 

 crabs above six inches in breadth continue to cast once in 

 two years, and it is probable that this is the case until 

 ecdysis stops. This rule cannot be an invariable one, as 

 there are a few records of male crabs which have not 

 undergone the casting process for at least three years. 



My suggestion that the males above six inches cast 

 more frequently than the females of a similar size, and, 

 therefore, do not become " grannies," is borne ont, not 

 only by an examination of the statistics given above, but 

 also by some figures which I quote from Williamson.* 

 These figures give a comparison of hard and soft mature 

 crabs taken off Dunbar. I have only included those 

 figures dealing with the casting period. 



Date 



Hard crabs above 4Jins. 



Soft crabs above 4Jins. 





Males. 



Females. 



Males. 



Females. 



Aug. 4, 1899 



26 



76 



83 



269 



117 



196 



60 



77 

 104 

 160 

 206 



60 

 200 

 110 



1 



235 

 140 

 64 

 66 

 56 

 22 



8 



■"■**&• -*■} j- ww 



Sept. 23, 1899 



144 



Oct. 27, 1899 



87 



Nov. 5, 1898 



32 



Nov. 17, 1899 



48 



Dec. 13, 1899 



42 



Dec. 20, 1897 



4 







Totals 



827 



917 



584 



365 







Total number of males 1,411 



,, ,, females 1,282 



In other words, for every 100 males (hard and soft) 

 there are 91 females (hard and soft). For every 100 soft 



* Williamson. Eighteenth Report, page 102, Table V. 

 HH 



