10 



It has been frequently pointed out before that the migration of 

 the female crabs to the north is correlated mth the di*ift of the 

 larvae to the south. It is evident from what has already been 

 said that the larvae mil come to rest all along the coast to the 

 south. As the j^oung crabs grow they probably migrate into 

 the regions of the coast in which they mainly abound, or are pre- 

 served in such regions which afford them protection and food. 

 At all events, while we know they annually migrate out and in 

 with relation to the coast they do not do so m the manner which 

 accounts for the distribution of dabs and plaice for example.* 

 The crab illustrates well the general principles of migration with 

 relation to current. Denatation is usually followed by contrana- 

 tation at maturity. 



* Report, Dove Marine Laboratory, New Series, III., page 29. 



