CHAP, xxi.] SECONDARY SYMMETRY : CRUSTACEA. 



531 



cases of repetition of parts in Crustacea. Including examples 

 recorded by various authors and specimens in different Museums 

 there are nearly fifty cases of this class known to me. 



FIG. 184. Three cases of two extra dactylopodites arising from a normal 

 dactylopodite. I. Left chela of Carcinus manas in Brit. Mus. II. Left chela of 

 C. mcenas after LUCAS, Ann. Soc. ent. France, S. 2, n. p. 42, PI. I. jig. 2. III. Eight 

 chela of Homarus, after VAN BENEDEN, Bull. Ac. Belg., S. 2, xvn. p. 371. 



FIG. 185. Cancer paimm*. Two chelte of the kind specified in No. 818, 

 described by myself in Proc. Zool. Soc., 1890, p. 581, whence tigs, are taken. 



342 



