LIFE HISTORY OF THE BLUE CRAB. 411 



bay and the adjacent ocean are covered with dead crabs, mosth^ oviger- 

 ous females. All the observers mentioned the late fall as the time of 

 such an occurrence. jSIoreovcr all those engag-ed in the crab fisher}^ 

 unite in saying that the}' have seldom, if ever, found an ovigerous 

 female shedding her shell, and that the females which are found early 

 in the season are of the virgin form. Evidently all the large females 

 of the early spring are slich as did not find a mate during the preced- 

 ing season and have, therefore, still to fulfill their maternal destiny. 

 It has been stated by Paulmier (1901) that the female cral) does molt 

 again after the eggs are hatched. His investigations made in the 

 neighborhood of Long Island may indicate strikingly different life 

 histories for northern and southern crabs, for the observations made 

 at Crisfield prove quite conclusively that the female does not cast her 

 shell after having produced her first and only lot of eggs. 



MOLTING. 



In practicall}^ all the lower animals whose bodies are incased in a 

 tough unyielding covering extension in size and an}" change of form 

 occurs not gradually and continuously, but suddenly and at intervals, 

 and is always preceded by the casting off of the confining skin or 

 shell, a process known as molting or ecdysis. The molting of the 

 crab might have been dwelt upon more fully in the preceding para- 

 graphs, but it is a matter of such interest and of such vital importance 

 that it deserves to be considered by itself. It must suffice, however, 

 to describe the process in the fully formed crab, and leave the subject 

 of the larval molts for future investigation. 



As the crab approaches the shedding period it begins to show its 

 condition by various external "signs," which are well known to the 

 fishermen and are of great importance to them. The first indication 

 is'a narrow white line which appears just within the thin margin of 

 the last tw^o joints of the posterior pair of legs. This line is so nar- 

 row and so obscured as to be bareW visible, bat it is immediately 

 detected by the expert, and the individual bearing it is classed as a 

 '*fat crab,'' or more vulgarly as a '' snot." Within three or four days 

 the white line gives way to an equally narrow and obscure red line, 

 and a set of fine white wrinkles makes its appearance on the blue 

 skin between the wrist (carpus) and the upper arm (meros). Such a 

 crab is known as a "peeler," and may be confidentl}' expected to cast 

 its shell within a few hours. As the time progresses the marks 

 become more and more evident, and a reddish color (especially in vir- 

 gin females) begins to appear at the margins of the segments of the 

 aMomen. Then, on the under surface of the carapace, extending 

 from the ncighlwrhood of the mouth around the sides and backward 

 to the posterior margin, there appears a narrow fracture, so that the 

 whole upper surface of the shell can be raised up from the back like 



