of the Fishery Board for Scotland. 173 
female, 43:7. The inclusion of the other males and females just noted 
reduces the averages to—Males 51:1 mm., and females 39°3 mm. 
Three crabs (Nos. 3, 10, and 11) lived to complete their third year. 
They measured respectively—Male 59°5, female 55:55. The crab No. 
17, which was 62 mm. broad in its second year, did not cast again 
during the succeeding twenty months ; it died soon after that interval. 
60 mm. may be taken as the size of the three-year-old male and 55 
for the three-year-old female. 
The conclusions regarding the rate of growth of the crabs under 
discussion are as follows :-— 
1 Year, 8-22 mm. Average 13°5 mm. 
_ {do 45-56 mm. 3 51 mm. 
See { 9 35-48°5 mm, weraee 9 39 mm. 
3 60 mm. 
os { 2 55 mm. 
Meek estimates the rate of growth as follows :-— 
One year, average 9 mm.: two years, average 37 mm.: three years, 
average 55 mm.: four years, average 69 mm. 
The discussion has rested principally on Waddington’s series, and of 
these the specimens which were got at a very early stage are especially 
valuable. The larger crabs which were introduced into the second year 
division had, by their subsequent growth, apparently justified the 
arrangement followed. 
The number of specimens under consideration is small, and it is 
difficult to know how far the conclusion may be legitimately applied 
directly to the crab in nature. A considerable amount of variation was 
shown in the growth of the crabs in their first year, and this it may be 
taken for granted occurs in nature, possibly to as great a degree as in 
the confined crabs. In the second year there was a tendency to eliminate 
the differences, a hastening of the development in the backward 
specimens up to the level of the more forward individuals. 
It appears very probable that the results will agree on the whole very 
closely with the life of the crab in the free state. 
Movrtinc—TuHeE Ratio or INCREASE. 
The number of moults through which a crab passes in a year appears 
fairly constant. Thus during the first year they were 8 to 11 in 
number; in two years, 14 to 17; and in three years 16-18. That 
moulting does not depend on the supply of food alone is apparent from 
the fact that the ratio of increase is so variable, vide Tables [. and II. 
The ratio of increase, that is the actual increase (mm.) at a moult, divided 
by the previous size of the crab, varies from j/, to 2: it is very often 
about z. In the earliest stages the moults follow one another rapidly, 
sometimes two (¢.g. Nos. 7, 18, 19) or even three (No. 20) occurring 
within a month. The rate of growth decreases with age (Meek). The 
Tables do not show a regular decrease in the ratio, but the decrease in 
the rate of growth is effected by the less frequent moulting or its cessation 
altogether. 
EARLY SPAWNING. 
Two females, Nos. 3 and 10, extruded their eggs in winter before the 
end of their third year. One of them extruded its eggs the previous 
