SEA-FISHERIES LABORATORY. 345 



As pointed out by Vitzou,* the method of ecdysis in 

 the Macrura differs from that found in the Brachyura, 

 because in the latter the abdomen is withdrawn first. In 

 the Macrura the thorax is first withdrawn, and the 

 abdomen leaves the old shell last. 



The tissues of the animal become greatly changed 

 immediately before ecdysis. The blood increases 

 enormously in volume, and Wittent suggested that the 

 increase is due to the absorption of water by means of the 

 digestive gland. He presumed that this excess of blood 

 plasma produced the internal pressure necessary for 

 ecdysis and growth. The muscles become very soft and 

 semi-fluid, and the fibres lose their well-defined outlines 

 and cross-striations. 



The digestive gland probably increases in size during 

 ecdysis. The fat cells are stocked with glycogen, the 

 ferment cells are much bigger, and the colour of the 

 ferment vesicle is of a deep brown colour, thus giving 

 the digestive gland a deeper colour at this period. 

 The reproductive organs are generally in an immature 

 condition at the time of ecdysis. 



Immediately before and after ecdysis the crabs are 

 unfit for food. They are kk watery " and have a bitter 

 taste. Reference is made in the Economic section to the 

 " Granny " crabs, which are considered by the fishermen 

 to be diseased crabs. I have reason to believe that they 

 are merely crabs preparing for ecdysis. 



One of the most interesting changes which accom- 

 pany ecdysis is probably the formation of the new integu- 

 ment, as a result of the extreme activity of the 

 epidermal cells. This new exoskeleton is already formed 

 when the hard shell is discarded. 



* Vitzou. Arch. zool. exp. et gen., T. X, 1882. 



f Report on the Scientific Investigations, Northumberland Sea- 

 Fisheries Committee, 1903. 



