116 



NATURAL HISTORY OF OUR SHORES 



life, sending its branching threads into the innermost parts 

 of the unlucky crab's anatomy whence it derives its nourish- 

 ment. 



The baglike body is often little more than a mass of 

 eggs, or Naupli, ready to commence their career. 



The " Cypris " of this species, once that stage is reached, 



Fig. 46. Acorn barnacles on the back of a large spider crab 

 Natural size 



swims the sea, prospecting, not for a log of timber, but for 

 a crab, upon which it can quarter itself for life. 



Comparatively few, however, can find a host in proper 

 time, and the majority of the brood come to an untimely 

 end. 



The Entomostraca. These are crustaceans, usually of 

 small size, although the " Great King Crab " (Limulus) 

 of American coasts is by many placed with them. 



The Trilobites that figured in the earlier history of the 



