Vv" of the Fishery Board for Scotland. 91 
TABLE sHow1ne tHE NUMBER OF CASTS IN EACH MOonTH. 
use |b = oe 
EE by = Pm evo) 4] = ° > 
o, as] = = 5 4 5 ° 
qe) Se shes | a a roe ey 
es ee | Sal ae ——————— 
Number of Casts | 3 1 1 l 
of each Sex 9 1h Wee 5 5 1 
Total for month .. Te [et ea eral EZ 2 5 5 2 
So far as the class of female lobsters here dealt with is concerned, 
there are two fairly distinct casting seasons. One, which is at its maxi- 
mum in July, claimed those females which were not berried during the 
previous winter,* while the second is an autumn casting season, the 
principal months being apparently September and October. In the 
autumn season those females that were berried during the previous winter 
and spring cast ;* that is to say if they cast at all during that year. The 
two seasons overlap, however. On September 2nd one of the first class 
of lobsters cast, and the list includes, for August, one of each class. 
_ The two cases in which the lobsters cast two years in succession, Viz. 
Nos. 11 and 12, are interesting, from the fact that the view has been held 
that the adult lobster would not cast two years in succession, Appellof 
maintains that view. The frequent castings of Brook’s specimens and of 
the two males recorded above are important as indicating a possible 
divergence in rate of growth from the female. 
It certainly seems that in captivity the casting process becomes more 
frequent than in the case of the lobster in the sea, The inactive existence 
of the creatures, and the absence of any search or exertion on their part 
in the quest for food, may have predisposed them to vegetate in place of 
reproducing. The food supplied was not excessive in quantity ; it con- 
sisted of shelled mussels (J/ytzlus edulis) and fish. 
The Increase in Size on Casting. 
One fact has been noticeable in connection with the moulting that 
occurred at the Laboratory, and that is the small increase in size that has 
followed the casts. 
It is sometimes difficult to accurately measure the moulted shell, owing 
to the rupture of the connection between the carapace and the abdomen 
which oecurs during the change, but care was taken to replace the parts 
as nearly as possible in their natural relationship before measurement. 
In the following Table the sizes of the lobster before and after the moult 
are set forth. Asa rule, the soft lobster was measured within a day or 
two of the cast. All the lobsters in the Table are females. The lobster 
is measured from the tip of the rostrum to the hind edge of the telson. 
* There was one exception. One female which was berried during the winter cast 
in the July following. Vide p. 87 
