488 O. W. HYMAN 



Megalops and crab stages. The specimens of megalops were 

 taken most abundantly in surface tow from the ocean just out- 

 side the inlet. They were also taken in numbers from crevices 

 in rotting boards exposed at low tide, under oyster shells and 

 stones, or from the bark on pilings. The crab stages do not 

 appear in the tow. They may be picked from the old boards, 

 with the megalops stages, or obtained during ebb tide on a sandy 

 beach (where they are very hard to see) or in the debris in the 

 marshes. After the crab measures about 2 mm. across the cara- 

 pace, it digs its own burrow and may then be collected by dig- 

 ging. All of the crab stages are found mingled with the adults. 



HISTORY OF THE DEVELOPMENT 



From the foregoing facts the following history of the develop- 

 ment may be deduced with reasonable assurance. The egg- 

 laden females remain hidden in their burrows during the day, 

 probably because the egg mass retards their movements to such 

 an extent as to endanger their existence. At dusk, when the 

 eggs are ready for hatching, the females approach the water's 

 edge and the eggs are hatched in the water. The larval skin 

 with which the embryo is covered is shed in hatching. 



The young zoea wobbles off on the surface of the water, being 

 carried along largely by the tide. Its own efforts, however, serve 

 to keep it at the surface, all the zoeal forms being positively pho- 

 totropic. After about four days the first molt occurs. The 

 second zoea behaves like the first — keeps itself near the surface 

 of the water by the rapid beating of the maxillipeds and is swept 

 along by the tides. After four or five days a second molt occurs. 

 The third zoea is the form most rarely found in the tow. This 

 indicates the possibility that it swims at an intermediate depth, 

 the maxillipeds not being strong enough to sustain at the surface 

 the increased weight of the body. 



After the molt to the fourth zoeal form, the zoea sinks. It 

 does not lie or crawl on the bottom, but is swept along by the 

 current and at short intervals drives itself upward by the rapid 

 beating of the maxillipeds. As soon as the maxillipeds cease 

 beating it falls slowly to the bottom again on account of its 



