SECT. VII. 



DECAPOD CRUSTACEA. 



195 



The eggs of the Brachyura are attached by gluten to 

 the false ciliated feet of the tail of the female, which 

 being bent up under the body forms a temporary protec- 

 tion till they are hatched. On leaving the egg the young 

 have not the smallest resemblance to the parent; it is 

 only after the fourth moult that they even acquire the 

 crab form. When the young of our common shore crab, 

 the Carcinus mcenas, leaves the egg, it is scarcely half a 

 line in length. The body is ovoid, the dorsal shield large 

 and swelled (fig. 148, A). On the middle of its upper 

 edge there is a long, hollow spine bending backwards, in 



A. 



^ih 



Fig. 148. Young of Carcinus mcenas in different sta v sres of development: A, first stase ; 

 B, second &tage ; c, third stage ; D, perfect form. 



which the white blood may be seen to circulate with a 

 sufficient microscopic power. In front there is a pair 

 of large sessile eyes, and the circumference of the pupils 

 is marked by radiating lines : behind, there is a long, 

 six-jointed tail, the last segment of which is forked and 

 spined. On each side of the shield there is a pair of 

 swimming feet attached to its waved margin. Fixed 

 also to the margin, but in advance of these, there are 

 three pairs of jointed feet ending in slender hairs. Im- 

 mediately in front, between the eyes, there is a very long 

 compressed appendage, which is bent backwards between 

 the claws when the animal moves. Under each eye there 



o2 



