of the Fishery Board for Scotland. 



121 



Notes on Casting, Distribution, etc., of Cancer pagurus. 



The Periodicity of Spawning and Casting. — Certain berried crabs 

 were obtained during the summer of 1902. Their eggs hatched during 

 August, September, and October. None of these crabs spawned again 

 until the end of October 1903, when two did so. None of the crabs 

 cast during the period. 



In February 1904 two of the crabs were berried, and two were found 

 dead. In the two latter the ovary was spent in one, and in the other 

 was ripe but dropsical. 



The Colour of the Soft Crab. — When a crab has just cast it is a 

 plump inert mass, which yields in all its parts to the slightest pressure of 

 the fingers. It is of a dark purple colour all over the dorsum and dorsal 

 surfaces of the pereiopods : the ventral surface is yellowish white. As 

 the shell hardens the dorsum gradually becomes of a lighter hue, turning 

 into a brick-red colour. Meantime the third or white layer of the shell 

 is thickening. 



In the paragraph dealing with the migration of crabs the question of 

 the abstention from casting is discussed in connection with one of the 

 labelled crabs. 



Casting. — During the autumn of 1902, 31st August to 15th October, 

 a number of female crabs cast in the tanks at the Bay of Nigg. With 

 the exception of the first, all the females recorded in the following Table 

 cast at this time. The size of the crab before and immediately after 

 casting is shown in parallel columns opposite the date when the cast took 

 place. 



[Table. 



