452 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



have changed a little too. They are borne on stalks now, and these 

 may rotate slightly in the groove in which they lie, although they can 

 not be raised from the groove. 



Of the hundreds of zoeas hatched and set adrift with the tide, less 

 than half live long enough to pass through the first molt. Many are 

 eaten by small fishes and jellyfishes. Others are swept ashore by 

 the tide and may form a part of the food harvested from the sand 

 "windrows" by the old fiddlers. Others become entangled in bits 

 of algae and other debris that float on the ocean and die there. The 

 survivors that become zoeas of the second order continue to float with 

 the tide and feed continually. After about a week they have again 

 outgrown their coat and then undergo the second molt. 



When the third zoea (figs. 14 and 15) comes swimming back to the 

 surface it is again larger and heavier and as a compensation the 

 swimming hairs are again increased in number, the exopodite of each 

 maxilliped now carrying eight of them. The weight of the body 

 has increased, more rapidly than the power of the maxillipeds, how- 

 ever, and it is more difficult for the third zoea to keep at the surface. 

 It sinks faster when the maxillipeds rest and they drive it more slowly 

 upward. Besides its increase in size the body shows other changes. 

 The chitinous coat becomes spotted with centers of calcification and 

 the shell begins to harden. The dim beginnings of new organs appear. 



On the straight spike of the antenna a tiny knob appears just at 

 the base of the exopodite. (Fig. 12.) This is the primordium of 

 the flagellum that forms most of the antenna of adult fiddlers. Be- 

 hind the bases of the second maxillipeds a series of tinjr buds appear 

 on the sides of the body. They appear in the region that represents 

 the thorax of the adult, and they are primordia of the third maxilli- 

 peds and the first four pairs of pereiopods or walking legs. The 

 buds of the first pair of pereiopods are noticeably larger than the 

 others. They will later become the pincers. On the lower surface 

 of each of the abdominal segments except the first there now appear 

 two small buds. These are the primordia of the later larval swimming 

 organs or pleopods. 



After another week of feeding and growth a third molt occurs and 

 the fourth zoea is formed. The fourth zoea (fig. 16) is just twice 

 as long as the first zoea. It is getting large enough now to be seen 

 readily with the unaided eye although it is still only 2 millimeters 

 long with the tail extended. All of the primordia that made their 

 appearance in the third zoea have grown larger and the buds of the 

 fifth pereipods have appeared. The telson is now separated from 

 the fifth abdominal segment by a joint. The growth of the body 

 and especially the development of the primordia have made the fourth 

 zoea rather awkward and clumsy. The swimming hairs on the max- 



