of the Fishery Board for Scotland. 91 



TABLE showing the Number of Casts in each Month. 





Sex. 



April. 



May. 



June. 



J uly. 



August. 



September. 



October. 



November. 



N umber of Casts \ 

 of each Sex [ 



6 

 $ 



1 







1 

 11 



2 



5 



5 



1 

 1 



Total for month 



1 







12 



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 (Mytilus 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 occurs 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. As a 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. 



