412 



EEPOKT OF THE COMMISSIONER OF FISHERIES. 



a lid, to expose the soft body beneath. Such a crab is termed a 

 " shedder " or a "buster." (Plate iii.) At this time the animal usuall}^ 

 lies motionless, but if disturbed is still capable of movement, and may 

 crawl or swim slowly away. It is incapable of showing any great 

 muscular force, however, and can inflict onh" an insignificant pinch 

 with its claws. 



The actual casting of the shell is now a matter of onh^ a few min- 

 utes; a quarter of an hour will usuallj" suffice, though the operation 

 may be prolonged to three or four times that period if the crab is dis- 

 turbed or if it is suffering from some recent injury. In the latter case 

 "it is often unable to complete the process and dies. By convulsive, 

 throl)bing movements the hindei- pair of legs begin to be withdrawn 

 from their encasement and are finall}^ freed. Meanwhile the other 

 legs have been started out and the body has begun to protrude more 

 and more from the shell. At last everything is out except the front 

 of the body and the large claws, but the latter, on account of the great 

 discrepanc}' between their size and that of the narrow articulations 

 through which they must be withdrawn, require some further effort 

 before the}^ can be freed. The thing would hardly be possible at all 

 were it not for the fact that on the upper surface of the hirge segment 

 of the arm (meros) a broad triangular surface of the shell becomes 

 loosened and rises up like a flap to make way for the crowded tissues 

 within. Some of the hard shell of the other lower (proximal) seg- 

 ments also seems to become softened and elastic So that by a steady 

 pull the great pincers are finally drawn through. Thus the crab has 

 backed out of its shell and meanwhile it has grown, for if it is caught 

 and measured it will be found to be considerably larger than it was 

 before.'* (Plate iv.) 



The skin is soft and the animal looks and feels flabby and helpless. 

 The back is wrinkled, and the "horns," or large lateral spines, are 

 curled curiously forward. Within a few minutes, however, the body 

 fills out, the horns straighten, and the growth at this interval is com- 



« The followino; measurements will show the increase in size for ci'abs nearly- 

 mature. The specimens were taken from floats at Crisfield and were selected at 

 random from among a large number. An effort was made to secure measurements 

 of smaller individuals as well, but the lateness of the season made it impossible. 



Sex. 



Female 

 Do. 

 Do. 

 Do. 

 Do. 

 Do. 



Se.x. 



Female 

 Do . 

 Do . 



Male . . . 

 Do . 



Before 



shedding 



from tip 



to tip 



across 



the shell. 



Inches. 

 i 

 4 



3| 

 35 



After 

 shed- 

 ding. 



Inches. 

 5 



4i 



4J 



