378 Proceediyigs of the Royal Physical Society. 



lobster agree in the main with those of Ileaumur. The new 

 limb is formed as a protuberance beneath the pellicle en- 

 veloping the scar, and, so far as my experience goes, this 

 reproduction always takes place from the basal joint. 

 Eeaumur's observations, however, appear to show that in the 

 crayfish, when the new limb has attained a certain develop- 

 ment, the membrane enveloping it bursts, and the limb thus 

 set free increases rapidly in size and secretes a shell for 

 itself. In other words, I am led to conclude, from a perusal 

 of Eeaumur's paper, that the limb may be liberated prior to 

 ecdysis. I am not aware of any criticism of this view by 

 other investigators, but Chantran would seem to imply that 

 the new limbs are only set free during ecdysis. Huxley, in 

 his work on the Crayfish, also states that the new limb is 

 set free at the next moult, but gives no reason for differing 

 from Eeaumur. 



In the case of the lobster the limb is undoubtedly set free 

 during ecdysis, and at that time only. The membrane in 

 which it was enclosed remains attached to the exuvium, and 

 though it is frequently ruptured, I am inclined to think that 

 this is sometimes, at any rate, only an accidental occurrence, 

 due to the thinness of the membrane itself. In the young 

 lobsters observed, the rudimentary chela, while still within 

 its envelope, appears to attain a length of from IJ to 1^ 

 inches. After ecdysis the limb swells out rapidly, and v/hen 

 the shell has been formed has attained such a development 

 that the terminal pincer joint now measures from 2 to 3 

 inches in length. Such a new limb will invariably be 

 smaller than the one which was lost, or than its fellow. 

 With each succeeding ecdysis the newly formed limb in- 

 creases more rapidly than its fellow in size, so that after a 

 number of ecdyses the disproportion is lost. The time re- 

 quired for a newly formed limb to attain its full development, 

 doubtless depends to some extent on the age of the lobster. 

 An old specimen, having larger chelate limbs and undergoing 

 ecdysis at greater intervals than a young one, will necessarily 

 require a longer period to complete the development of lost 

 parts. The specimens I had under observation were all 

 immature, and the two which supply information on this 



