200 On the Common Shore- Crab, 



of ecdyses a specimen of any given size may have gone 

 through. The Table may not, therefore, be scientifically 

 accurate, but will serve my purpose. The measurements in 

 themselves are correct ; but I cannot, of course, be sure that 

 specimen P, for example, which was 5x6 millim. when I got 

 it, had already cast its shell five times from the Megalopa ; but 

 the measurements appear sufficiently near to those of A and 

 B at that stage to warrant me in concluding that, at any rate, 

 I am not far off the mark. 



The dates corresponding with the above ecdyses are as 

 follows : — 



A and B have been already given. 



Z. 19. vni., '2. IX., and 15. ix., 82. 



No. 8. 25. IV. and 28. v. 83. 



P. 3. VII. 82, 29. VII., 16. viii., 10. ix., 1. ii., 83, 16. v. 



B'. 2. VI. 82, 23. VII. and 25. v. 83. 



D. 22. IV. 82, 10. VI., 21. vii. 



C. 17. IV. 82, 8. VI., 16. VII. 



N. 18. vu. 82, 17. VIII., 2. x., 5. ii., 83, 21. v. and 21. viii. 



M. 12. V. 82, 12. VI., 16. vii., 17. viii. 



Y. 4. IX. 82, 5. X., 28. xi., 27. ii., 83, 15. vi. 



(a). 3. IX. 82, 7. X., 2. II., 83. 



It will be seen from the above dates that out of a record of 

 fifty-four ecdyses there is only one that occurs between the end 

 of October and the beginning of February, while the majority 

 are in the summer months. D and C cast their shells 

 about the same time, and increased to about the same extent 

 at each ecdysis. Y, on the other hand, was only the same 

 size in September which D and C had attained in May. 

 Again, comparing N and Y, the former only increased from 

 15'o millim. to 45 millim. in ten months, whereas the latter 

 grew from 14'5 to 56 millim. in nine months, and with the 

 same number of ecdyses. 



It would appear, then, impossible to judge either the age 

 of any particular specimen or the number of ecdyses which it 

 has passed through from a casual observation of it on the sea- 

 coast, and even in confinement a number of ecdyses must be 

 passed through before any reliable information is obtained. 

 B'', for instance, passed through two ecdyses in the summer of 

 1882, and then did not cast its shell again until May 1888. 

 N & Y, on the other hand, grew considerably larger than B' 

 without any such break. In attempting to guess the size 

 A and B would be two years after hatching, A may be taken 

 as a backward form, which would perhaps follow tlie ecdyses 

 of such a form as P. In that case, next June, A would 

 measure about 28 millim. long by 35 millim. broad. If B, 

 on the other hand, which is a strong forward specimen, should 



