IV 



of his observations and experiments undertaken, during the 

 period of this inquiry, with a view to elucidate the subject. 



In the earlier stages of their development, these Crustacea, 

 like all others, assume forms which are totally dissimilar from 

 their subsequent appearance. But, when all their metamorphoses 

 are complete, their subsequent growth is still marvellous. The 

 crab measuring an inch across its back, the lobster measuring 

 an inch in the barrel, are as perfect in form and structure as the 

 largest crabs and lobsters. Both the crab and the lobster 

 in their minutest forms are surrounded with a hard calca- 

 reous armour-like tegument. The covering cannot by any 

 possibility expand ; and how is it possible for the animal to 

 grow without increasing its shell ? The problem is solved by the 

 creature withdrawing itself entirely from its shell, having pre- 

 viously secreted a new and larger covering for its future use. 



A most remarkable circumstance connected with tins episode 

 in the natural history of the higher Crustacea is that the animal, 

 when it withdraws itself from its shell, is always considerably 

 larger than the shell from which it is withdrawn. Since the soft 

 new shell, in which the creature is already encased, immediately 

 commences to harden, its growth could be effected by no 

 other arrangement. But the marvellous fact still remains, that 

 the creature is enabled to withdraw itself from its cast shell, and 

 that the shell from which it has withdrawn itself is as perfect 

 and unbroken as ever. 



The plates which accompany this report will show, more 

 distinctly than mere words can express, the growth of the crab 

 on casting its shell. (Plate No. 6.) 



It would materially have facilitated our labours if we had any 

 reliable data to show at what periods crabs and lobsters cast 

 their shells. We reproduce, for this purpose, the observations of 

 a French naturalist on the subject^ which have already appeared 

 in the Report on the Fisheries of Norfolk.* These observations 



* According to some careful observations made at the Marine Laboratory, Con- 

 carneau, it appears that, the first year, the lobster sheds his shell six times, the second 

 year six times, the third year four times, the fourth year three times. 



The following table shows the rate of growth in a lobster after each shedding of 

 its shell : — 





Sheddings. 



Length. 



"Weight. 









inches. 



ozs. drachms. 







8th 



2 



- If 







9th 



H 



— n 







10th 



*k 



H 







11th 



3 



~ 5 f 







12th 



H 



— H 







13th 



4 



— 104 







14th 



H 



i 4 





{Vide Parliamentary Paper, No. 428, Session 1875.) 



