366 



ANIMAL LIFE-HISTORIES 



It will have been gathered from what has already been said, 

 that development is direct in some of the Higher Crustaceans, 

 but the stalk-eyed forms usually hatch out as larvae. This early 

 free-swimming stage in the life-history is, however, but very rarely 



Fig. 889. — Life-history of Edible Crab [Cancer pagurtis), enlarged. A, Young Zosea. b, Fully formed Zoasa. 

 c, Megalopa. D, Young Crab (during life the tail is bent up under body). 



a Nauplius, the most characteristic variety of larva being the 

 Zoa;a, which is partially segmented, and otherwise of more com- 

 plex nature. In the life-history of the Edible Crab (^Cancer 

 pagitrus, fig. 889), for instance, the just-hatched Zoeea is a rather 

 ungainly-looking little creature, with large rounded cephalothorax. 

 {i.e. head and thorax fused together) and slender limbless tail (a). 

 The large appendages shown in the drawing are foot-jaws, which 



