MIGRATION OF CRABS. 



By ALEXANDER MEEK. 



The results of the marking experiment of 1912 have been verj?- 

 successful, as has been manifest from the precedmg reports. The 

 crabs were marked with characteristic care in the last three months 

 of 1912 by the late Mr. John Douglas, Beadnell. Forty-one females 

 were recaptured, and in nearly every case they had migrated north- 

 wards, the majority having reached Scottish waters.* 



This year, thanks to Dr. T. W. Fulton, of the Scottish Fishery?- 

 Board, we received No. 257, a female marked and hberated on 

 October 16th, 1912, at Beadnell. It was caught, presumably in 

 a cod-net, on March 16th, 1916, one mile off Banff, a distance of 

 about 160 miles from the place of hberation. It measured across 

 the carapace 18 cm. (7 ins.). This example has been absent there- 

 fore for 3 years and 5 months. The specimen presents several 

 interesting features. 



It was a berried female. This is the first time that a berried 

 crab has been returned in connexion with the marking experiments. 

 The berried crab is not often caught in a crab pot, and this is due 

 Ukely to the great distention caused by the enormous mass of eggs, 

 and also probably to a disinclination to feed. The eggs had been 

 recently spawned, for development was only shghtly advanced. 

 The spermathecae were found to be empty. 



The next point is that the cuticle or shell had been retained 

 for a period of nearly four years. There is now abundant evidence 

 from the Northumberland experiments of the variabihty in the 

 periods intervening between successive ecdyses, and the probable 

 cause of the retention of the cuticle has been discussed in previous 

 reports. It is not likely in this case that the usual routine had 



* Report?, Dove Marine Laboratory, New Series, II., 1913, page 13 ; III,, 1914, page 

 73 . IV., 1915, page 40, 



