FIDDLER CRAB — HYMAN. 457 



distributed. These continue to multiply from this time on and later 

 arrange themselves into the definite color patterns of the adults. 



The abdomen of the young crab is greatly changed. It, too, is con- 

 siderably flattened and it is carried permanently flexed under the 

 thorax as it is in the adult crab. The abdomen fits closely into a 

 groove on the under surface of the thorax. The pleopods of the 

 megalops are still present but they are sadly changed. Instead of 

 being powerful swimming organs they are mere wrinkled finger- 

 shaped sacs. They are almost empty of flesh and, of course, contain 

 no muscles. 



Since it can no longer swim the young crab must depend upon 

 its pereiopods for locomotion. During the megalops stage these were 

 used for clinging only and in the young crab they are conspicuously 

 more efficient for clinging to its refuge than for walking, and run- 

 ning is quite out of the question. The young crab has undergone 

 very little change in its sensory appendages and mouth parts. Each 

 appendage is somewhat larger and somewhat better adapted to its 

 physiological use. One or two new gills are beginning to appear 

 on the bases of the maxillipeds. 



More noticeable changes occur in the appendages of the posterior 

 part of the thorax. The fifth pereiopods have lost their long hairs 

 and are no longer carried tightly folded over the back. They now 

 have the sharp distal points of clinging legs and they still have a 

 tendency to turn up over the back. They are distinctly useful to the 

 little crab now, however, in clinging to an object behind it. The 

 fingers of the pincers are now just alike on both hands of all the 

 young crabs. They are of the same size and both fingers end in 

 rounded points that are hollowed out like spoons. They are well 

 adapted for picking up small objects and from now on the young 

 crab must get nearly all of its food by picking it up from the bottom 

 rather than seizing it in chase as the megalops did. Consequently 

 it begins to make for the shore where an abundance of food is washed 

 in by the sea and left in accessible places. The young crab is very 

 weak and awkward, but by clinging to any support that offers it 

 slowly gains the beach and crawls out on the land for the first time. 

 It does not leave the wet parts of the beach, however, but remains 

 down between the tide lines. Here they may be found crawling 

 around in considerable numbers during the latter part of the sum- 

 mer. They are very weak and awkward and even the tiniest wave- 

 let will roll them over and over. Accordingly they do not venture 

 far out on the open beach but remain hidden under the protecting 

 rim of a bit of oyster shell or water-logged wood or else cling to 

 tiny sedge rootlets that have been washed bare by the tide. The 

 crabs are very helpless, but are almost invisible on the damp sand 

 where they live. 



