CRABS AND SHRIMPS. 



185 



other, and the tail is flexed on them so far as the margin 

 of the shield, and, if long enough, is reflected over the 

 front of the shield between the eyes. The dorsal spine 

 is bent backwards, and lies in contact with the dorsal 

 shield ; for the young, when it escapes from the egg, is 

 cmite soft, but it rapidly hardens and solidifies by the 

 deposition of calcareous matter in what may be called 

 its skin. The progress of this solidification may be very 

 beautifully observed by watching the circulation in the 



SECOND STAGE OF SHORE-CBAB. 



(Meijulopo.) 



-dorsal spine. When the creature has just effected its 

 liberation from the egg, the blood-globules may be seen 

 -ascending to the apex; but, as the consolidation advances, 

 the circulation becomes more and more limited in its ex- 

 tent, and is finally confined to the base. These minute 

 creatures, in this early state of their existence, are 

 natatory, and wonderfully active. They are continually 

 swimming from one part of the vessel to the other ; and, 

 when observed free in their native pools, are, if possible, 



