250 Dwellers of the Sea and Shore 



having a long curved spine standing out from the 

 middle of the back, and another straighter one pro- 

 jecting, like a beak, in front. The hind body is much 

 smaller. It is narrow, segmented, and ends in a forked 

 tail, or telson. It is also very flexible, and can be bent 

 under the fore body or straightened out behind. There 

 are several pairs of delicate appendages on the fore 

 body, but the most conspicuous are the two pairs of 

 swimming legs ending in featherlike branches. Actu- 

 ally, the tw^o-branched swimming legs are appendages 

 belonging properly to the mouth, the real legs of the 

 crab being not yet in evidence, and, although the seg- 

 ments of the abdomen are distinct, they are devoid of 

 swimmerets. 



This description of the first larval stage of the fiddler 

 crab applies with almost equal correctness to the newly 

 hatched larvae of every member of the marine Brachy- 

 X ^ ura, or crabs. It is a typical form and for that reason 

 N it is known as a zoea, a name which it received when it 

 was thought to be a separate and distinct species of 

 crustacean. Some land crabs differ slightly in their 

 earliest larval appearance. That the zoea were once 

 thought to be an independent species was due to the 

 fact that the development of the fresh-water crayfish 

 was known long before that of other crustaceans. In 

 that creature the young when hatched from the egg 

 are practically like the adult, and it was therefore 

 assumed that all crustaceans were developed alike. 

 Indeed, the larval stages of marine forms were known, 

 but their actual identity was not suspected. And even 

 after their true nature was discovered, after their 

 metamorphoses had been studied and described, many 



