57 
development of the abdomen in the two sexes, the acceleration in 
growth of that of the female, the retardation of that of the male is 
shown in each case in relationship to the carapace, and on the left 
of the chart the breadth as compared with the length. There is not 
much difference in the case of the two chelae in the young state, but 
the variation increases with age, and the variation appears, as we 
should expect, to affect the male more than the female. 
6. — Migeations. — So much has been done in our own district 
and so recently reported upon that a word is only necessary now 
under this head. The crab leaves the coast for the deeper and often 
extra-territorial waters in the autumn, returning gradually to the 
shore again in the spring, although it has been shown both by 
Williamson and as a result of our own experiments, that the crab at 
the same time may also migrate to some distance from its original 
location. So far as has been seen, this is always in a northerly 
direction. Crabs, said usually to be old and black, are occasionally 
caught by trawlers at considerable distances from the shore, so that 
they appear to migrate sometimes very far in that direction as well. 
It is not easy to explain this, though it may be that the blackness is 
caused by the soft ground so general off the coast. 
As has been said already the crab of the Southern District has 
not so much room for migration as that of the North, but we have 
no definite facts yet as to how far the soft ground really affects the 
migratory movements. 
Lobsters also migrate to a slight degree in the winter months, 
but as a rule do not go very far from the inshore hard ground, and 
the berried lobster appears to remain altogether inshore. In spite 
of this general rule we are told that on hard ground, .many miles 
from the land, lobsters are sometimes caught by trawlers. I should 
like to get one or two of them with details as to localities of capture. 
I may also take this opportunity of stating that further experi- 
ments are being made on the Northumberland coast to obtain some 
more facts with reference to the migrations of crabs. The labels 
bear the letter N followed by a number and are tied to one of the 
large claws (chelae). 
7.— POPULATION. 
1. — Lobstees. — The average annual catch of lobsters on the coast 
of Northumberland, according to the statistical returns for the ten 
years ending 1904, is 39,555, say 40,000. . 
